As T Robinson says, parole and probation are two different things, which may be handled by the same individuals or may be separate departments. One dirty urine is not likely to get someone returned to prison. I've seen inmates with a dozen dirty urines and not returned to prison. On parole, you can be returned to prison, or sent to the parole board for review of your status, or you can go in front of a judge. Different states do this differently.
If a parolee expects to be violated, he probably won't show up at the parole office. But usually a parole officer isn't going to give warning. But if someone is going, he's not going to be allowed to wander away. Factor into this the stupidity of your character. Usually what gets a violation is the police suspect something, but don't have enough for an arrest.
Most likely cause to scare a parolee is when he's out on parole, gets into a trouble with the police and either runs faster or they don't take him in, and knows that the police, once they figure it out, will be charging him with a new felony and as soon as that happens, he's violated on parole, so bail is not an option.
Another good option is when the parole officer does a home visit, parolee is not there, and parole officer finds his stash, or his old lady dumps on him. He sees or hears about this, know he's going to be violated as soon as his parole officer can find him.
Best of luck,
Jim Clark-Dawe