Exact situation happened to me. I was hired onto preload, worked 6 months there, passed packet and made FT driver. About 6 months into driving I got my benefits pkg....then looked into it and realized that I had not payed a single cent of union dues up to that point. Called my BA who had just left our building as a steward and he took care of it right away and didn’t charge me any back dues. Just make a couple calls, man. Sometimes stuff slips through the cracks