Is it just the lume filling or the whole marker ( including surround) that’s come away? If its the whole marker it can be re- attached but if its just the lume I’d be less hopeful. Possibly the marker could be relumed to match but getting an exact match would be a challenge. Picture would definitely help.
As for getting goodwill from Omega on a 19 year old watch?.......no chance in my opinion. They may offer to sell and fit a new dial.
Its unusual for this to happen, I’ve seen batons become detached on older watches but even that’s quite rare.