If you’d hung around they wouldn’t get on the track to fetch it. Against every rule in the book.
If it’s an electrified line with third rail even more so. They’re even instructed to not try to rescue someone who’s fallen on the track if electrified. Actually sensible as they themselves can be killed by touching the person. Seen similar where someone drunk climbed onto the track and passengers were getting irate with staff for not helping him off but then they had to hold passengers back who were trying to help the guy.
Anyway, likely to retrieve it they’ll have to wait for a particular time or during maintenance, and doubt they’ll be bothered. Unless it’s something they can stick in lost property as then they can charge people to claim their lost property.