What did the police come to your house for? It is not everyday that one gets a home visit from police.
If they just came to talk to you or someone in your household about what you know about something, then that would not be in the computer.
By "police contact", the probation department probably means anything like an arrest, a ticket, a stop for a traffic violation which resulted in a warning, etc. A discussion is probably not included but, that said, why would you not tell them if it was nothing? Why risk that my or your interpretation of police contact is wrong, and that somehow they find out (like the probation officer and the cop are friends and they are just talking shop one day and it gets mentioned.)