Same thing has happen to me, over 300 items. Put a few things into storage from a toon I planned on deleting. After deleting went back in to remove items to level a low level and all 8 containers were empty.
Disabled all add-ons, still gone. 2 days now.
I worked with support yesterday and they said I would need to provide a list of the items. There is no way I can do that, I haven't played for 6 months and was just starting back up. Ugh.
A search here showed this same thing happen back in 2018...
Will keep checking back here for updates.