Still don't see it's location or use, the spring/wire you removed.
The thumb bar spring on some is a small coil spring. On others it is part 22808. Unless an engineering change was made from your spring to the flat one. Shown on part # 220808 above.
If a parts source is located, the info on reel foot is required.
One mention of thumb bar sticking, besides cleaning , was to roll spool back an eighth inch or so before depressing it.
Imagine that's easier said than done with a fish on....