An endoscope is very useful in these situations.
I have used this one with the attached tools to retrieve dropped keys between the planks of a raised deck. I also used it to find a leak in a bathroom shower wall faucet.
USB Endoscope for OTG Android Phone, Computer, 5.5 mm Borescope Inspection Snake Camera Waterproof with USB, Type C, 16.4FT Semi-Rigid Cord with 6 LED Lights, Compatible with Windows PC, MacBook
https://a.co/d/iETVpJy