Your probation officer may find out. Probation normally includes a mandate that you report any new charges, so odds are he's supposed to find out from you. If your probation officer is asking you to verify each month whether or not you were arrested, quite obviously he expects a truthful answer. If you lie in your report, and are caught, I expect that your probation officer will initiate a probation violation hearing.

You chose not to identify either state involved. Laws vary by state. Consult a lawyer in whatever state and county are involved, so you can get a sense of how a probation violation of this type might be handled in that county.