I'm finally going to quit lurking to jump in here.
I'm a local, and my younger brother reminded me of this case over the summer after he took an ill-advised expedition to the barrel sites through Bear Brook State Park, up to the remains of the store. (Yes, I yelled at him for trespassing in the backwoods of Allenstown behind a trailer park, because there are many ways in which that could have gone horribly wrong.)
Interestingly, he did find a barrel back there, and sent me a picture of it. I'm assuming it's a more recent barrel--dumped after the last search of the property in 2000--but I've been thinking about it a lot since the new developments emerged...
Anyway, a few pages back on the thread, IllinoisMissing mentioned the Oakhill blog comments, and a how someone commented about a guy who worked at the store. YES. There are a few anonymous comments on there that are eerie, considering the information we now know. As soon as the press conference was done, I went back to confirm that they're still there, and I'd encourage anyone curious to check them out. The first few were posted by someone who was a resident of the trailer park briefly during the 80s--and it appears that the same person posted again about a year later, but I'm just guessing based on the anonymous commenter's grammar/syntax. There are two initial comments dated 1/13/15, and a followup on 1/15/15, by the same author. There is also the comment from 2/11/16, which appears to be the same author. Yes, some of the details are incorrect, but there are a lot of details that align with the latest information released by LE last week--in those comments from 2015. You guys might want to check them out. Even if they don't seem valid, they might help with the brainstorming.
I know it's been posted here before, but here's the link to the Oakhill Research blog:
https://oakhillresearch.blogspot.com/2012/07/crime-watch-daily-featuring-allenstown.html