I just spent the 400k sP on ten Treasure slots for my pet Widdershins from the TC page. After the page refreshed from the purchase, my pet still has 62 slots (previously had 62, all filled), but it appears that the sP has been spent. I've tried refreshing the pages multiple times, navigating away and back to the page, etc, but they still haven't showed up.
I'm using Google chrome from my Android, not sure of that's relevant...
Hey there! c: I experienced this issue myself just now. Have you filed a ticket yet? The staff was able to quickly refund my sp for this issue.