Tracing Mobile Phones & Planted Evidence

I have a scenario in my novel set in current day Australia where my good guy is forced to hand over his phone to a bad guy. In return, he is given some kind of disposable phone. He is then set up for a crime (kidnapping, child found safe and well) and arrested. This means the phone he is arrested with is not one that's registered in his name (or actually, it might also be. But in any case, there's another phone out there that's registered in his name that isn't in his possession). While this is happening, I want my baddie to play with good guy's original phone and install some sort of gps tracking device in it - whether its a chip or some sort of mobile phone app - I'm thinking the latter will be less detectable. I know my two brothers have iPhones and use a Find My Friend app to track each other's location. I then want my baddie to go back and plant the phone as evidence at the scene, where the cops can find it. He obviously wants the cops to find it, but I don't want them to find it in the initial search, but one cop on his own a couple of days later. This leads to a number of questions:

1. Would the area be cut off to the public and for how long (will my baddie be able to go and plant the phone as evidence without being noticed)? It's at nighttime, secluded area of public park, I'm guessing cops would want to see how things look in the daylight.
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2. I'm guessing the phone will need to be off until the bad guy plants it to prevent it being traced through mobile phone towers. I'm also guessing this wouldn't go unnoticed by police if they tried calling the number while it was off. Could the phone be turned on without the cops realising? For how long would they continue trying to call/trace the number? If they have the guy in custody and he is found with another phone, is there really any need for them to call/trace it in the first place? How likely is it to be missed in the search of the crime scene? I mean to say if someone is arrested, the child is safe, how thoroughly are they going to be looking at the scene? I figured I could hide it under some park bark, shadow of the trees, nighttime and have it easily go unnoticed, but not if they're going to be trying to call/trace it.

3. Phone is found. Would the police consider it evidence they missed in the search, or planted evidence? If they were calling it noticed it go on/off, I'm guessing they'd consider it planted, but if they didn't notice, would it be a matter of missed evidence?

4. Are there many popular phone apps that allow you to trace your friend's phones? Would there be a way of telling when an app was installed on the phone, or when a contact was added to the app? In police terms, how much of a threat do these pose, or could such a thing also go unnoticed for say 36-38 hours? Would it be less detectable than some kind of GPS tracking chip? I'm guessing they would probably be more interested in the message and call logs.. but depending on how long they take to sort through..

Thank you so much for your help! Sorry if that's in any way confusing - it probably is! But as soon as I started thinking about it, each question would lead to a new question... =P

Thanks Bufty, I'll take a look

Thanks amschilling To try and make things clearer... the bad guy wants to track where the phone is going, hence installing the app. However, if it's a standard app, it may have already been installed on the phone prior, and as such it's just a matter of the bad guy adding his number into the phone and into his phone (accept a request?) and I wonder if that sort of date would be recorded? The good guy who is arrested falsely confesses, and as such mentions nothing about his stolen phone. The police find the kidnapped child with the guy they arrest, and so there is no more missing child. The problem is I don't want the phone found in the initial police search of the scene, and I wonder how likely/unlikely that would be, and if it were to be found later whether it would be considered something planted or something they missed.

Thank you! Very helpful! I wasn't planning on returning the phone to the good guy, so that's okay =P I think I will leave the phone off, which makes things easier too. I guess then the last thing is how long it would take them to check the phone for call logs, messages etc, and how long it would take them to notice a seemingly harmless friend app (until of course they dig harder and find a time stamp on it made after the arrest)?

Aha! I didn't even consider the prints xD I don't think my bad guy is going to be too considered with wiping off the prints, but that means there's going to be two sets of prints on the phone. So if they're focusing on that, along with the calls, I daresay the app could go unnoticed..

Hi Mac - I will definitely look up those cases you mentioned as it sounds as though they could offer some helpful insight. A hidden app may also do the trick as you say. The area not being locked off also works to my advantage so he can actually go back and plant it.

Thanks so much guys