... has come off. I still have it. How can this be repaired, what should I expect to pay? Did this compromise the watch's interior? Thanks in advance.
Somehow the screw seems to have come undone (hopefully not broken) Did you notice the pusher cap working its way outwards before it finally came off? As the screw is put in from the inside of the case, there should not be enough clearance for it to fall out into the movement, unless it has broken and it is only the work of a few minutes to put it back together - say about half an hour. The thing to decide is whether or not you want it tested for water resistance. This would add to the time taken and may necessitate either replacing the seal inside the pusher, or the pusher itself. This would be dictated by where you take it (Omega or an independent watchmaker)
Just chiming in about the loss of Speedmaster push buttons... A colleague of mine had the same problem with the lower push button. Statistically it can be either button that has a problem but it seems the lower push button seems to win... although it the least one used. Even checked this NASA astronaut's Speedmaster (photo below) Yep lower push button missing... .
https://omegaforums.net/threads/speed-master-pusher-fell-off.90747/ Here’s what happened to mine this week