My suggestion is to pull out the seat post, turn the frame upside down in a workstand, and use a flexible "grabber" like THIS to see if you can reach up the seat tube, grab the ID tag with the grabber, and work it back down the seat tube with gravity helping you out.

It that doesn't work, you may have to remove the bottom bracket, and assuming there's a hole in the BB shell where the seat tube joins the BB shell, try to pull it out through the BB shell.