I've been having similar issues since Season 2 Update. I believe my 1st day (on launch) was fine, but the next day I logged in, a pop-up said I unlocked " skate. Insider rewards...for season 2".
When I redeemed the pack, it showed a few stickers that were already unlocked in Season 1: Surprised Llama, skate. Insider Ramp, skate. Insider Logo, skate. Insider Deck & skate. Insider Board.
Since then, I have not been able to see any stickers in slots 1,2 or 3 (including the one I spent SVB for).
*[update] I did "verify the integrity of the installed files" in Steam to see if something wasn't cached properly or something, but no luck there.
Otherwise, things have been pretty smooth...Anyways, I hope this info helps!
Thanks for everything so far, keep up the good work!