If the sticker under the seat is still there and the top layer with the numbers on it has gone you can still read it by aking some photos with a digital camera ( NOT A PHONE ) at several different angles in good light ( from one side only ).
Then load them into any photo editing app you can find
Increase the contrast & decrease the brightness.
Usually the numbers will pop out because the camera sees the difference between the faded base white and less faded bit where the printing was .
Last ditch effort is to invert the image ( make white black ) some times called "make negative "
I do this at least once a month