I lost something during my stay.
per-so — two syllables, stress on the first. Past participle of 'perdere'.
Report a lost item at check-out before leaving the hotel. Staff can check the room immediately.
'Ho perso' is the passato prossimo of 'perdere' (to lose). 'Durante il mio soggiorno' = during my stay. This is different from 'ho lasciato qualcosa in camera' (I left something in the room) — 'perso' implies you are not sure where you lost it.
Penso di aver perso il portafogli al ristorante dell'hotel.
I think I lost my wallet at the hotel restaurant.
Specify where you think the item was lost
Ho perso gli occhiali da sole, forse in piscina.
I lost my sunglasses, perhaps by the pool.
Different hotel areas have different lost and found procedures
Qualcuno ha consegnato un telefono trovato?
Has anyone handed in a found phone?
Ask directly if someone may have found and turned in your item
Italian hotels have a moral and in some cases legal duty of care for guests' property in common areas. If you lose something in a hotel restaurant or common area, report it promptly and in writing. Keep a record of the report for insurance purposes.