AtticGeneral, We have checked your account and did not find any Haunted Tanks for last year. None have been bought from the Marketplace and last year we didn't have the option of trading 10 masks at the end of the event for the special item.
You have gained special items for following events - Christmas and Easter - but not from the Halloween event.
Hope this helps.
Please contact us if there's anything else or regarding the current event.