Depends on the worth of the phone.
In my state up to $500 is a misdo so they cannot get more that a year in jail. The only people that would get that are multiple repeaters.
Over $500 the lowest felony (if no force was used), max just over a year in the penn and fines.
If the person only has possession and you cannot prove he is the one who actually took it then always a misdemeanor or possibly nothing if he, as a reasonable person, did not have a good way of restoring it to the proper owner (goes to knowledge of theft)