Apple Airpods mystery

Hello, I wonder if anyone can help me what has happened to my Airpods? I accidentally dropped them in the gym. I put them back in their case, closed it and they must have slipped out of my bag. When I returned to the gym a week later, I turned on Find my Iphone and there was a green ring around 'Sophie's Airpods' indicating that they were online within range of my phone. I started to search around expecting to find them, but there was no sign. I retraced my steps of the previous week and pressed 'play sound' hoping to hear a beep but of course a gym is very noisy with fitness machines and music so I found the manager and we walked around trying to locate them. We had no luck and there were lots of people with airpods and no one was removing them hearing a beep, that we could see anyway. I returned to the gym 3 more times that day and each time it showed a green ring indicating they were online. I finally went back as they were closing up and the music was off and it still showed they were 'online' but I could hear no beeping but it is a big place on 3 floors so I pretty much have given up hope of finding them. By this time everyone had left the gym apart from a couple of members of staff, though they could have been in a locker somewhere. When I returned the next morning I could see my airpods registering only a grey ring. Today I went back and 'Sophie's Airpods' are no longer even on my list of devices on Find my Iphone. Am I right in assuming that someone has found them, taken them home and erased my name from them?

It's been a frustrating end to the story, but wondered if anyone knows what no longer being on my list of devices actually means - erased or battery run out?

Many thanks!