Hello Heath
If it has not been treated as an express search request (and you consequently have paid CHF 50), it will follow the normal lost & found process. You have to fill in a lost property report and then it will be matched at the central storage for lost property. Due to the huge number of lost items, it may take up to three weeks to have it back, however.
https://www.sbb.ch/en/help-and-contact/lost-found-office/submit-loss-report.html
The fact that you were in contact with the police will not change a lot.
Alternatively, you can call the SBB Contact Center to check whether the lost property is still at Basel SBB and not already sent to the central storage:
+41 51 225 78 56 (24/7).
Customers cannot call station offices. The phone numbers are not public.
Kind regards,
Roland