Sounds like you got served from the same stash that stocks the Sky Clubs. There are reports that Biscoffs are no longer being served on flights <600 miles, although YMMV.
http://www.flyertalk.com/forum/delta...hased-out.html
From
delta.com:
250 Miles or more (up to 1.5 hours)
We offer complimentary Biscoff cookies on flights from 5:00am to 9:45am and pretzels on flights from 9:46 AM and later, plus a selection of complimentary nonalcoholic beverages.