I worked in the game dept at a TRU from 98-03, and we definitely never had the Wonderswan. We did have the NGPC, and I remember snatching up gobs of games when the whole thing went under, along with both of our kiosk/display systems for $4 each.
Good times.
I have always been a bit curious about the 'swan though. Seems to me I played with one at E3 back around that time, but I might be confusing it with the GP32.