Damn. RIP Chelsea. There have been so many high profile missing cases end badly this month
What was the industrial site used for? Anything to do with construction/roadworks, & how many guys at the party have connections to that kind of industry? Because it's quite a coincidence both sites of interest are industrial/construction-related when presumably there's a lot of natural area available.
ETA just read back over the thread again (instead of relying on months old memory) & the first site was used to store petroleum & then abandoned. I guess it could be linked by work if the residential builders had their tipper trucks dump soil over at the abandoned petroleum site, or if the petroleum site workers switched to construction after it shut down, but it's probably just places most of the town knew of.