Forgot my power bank in a cafe in Chiang Mai yesterday
Was working at that spot near the night bazaar. Left my Anker 20k on the table. Ran back 10 minutes later, gone. Had to buy a cheap local one for 300 baht that barely charges my laptop once.
Same thing happened to me in a coffee shop in Bangkok last year. Came back in less than five minutes and the staff said "no one took anything" but it was just gone.
The staff in Bangkok probably genuinely didn't see anything, not that they were hiding it. Those shops are chaotic and understaffed, things slip through the cracks all the time. It's easy to assume they knew something, but more likely they just weren't paying close enough attention.