"A tourist who camped by the lake only to have his expensive mountain bike vanish."
Probaly North Beach Campground. I stayed there for two nights in 2018 and last year. Both times during bike tours. There is relatively easy public access from the beach and the Island Line Trail that passes by the camping area., Although the gate that allows access to the camping area from the trail is closed and locked at night, it's still possible to access the camping area from the beach even though it is closed at night.
During my 2018 stay I was up late reading and saw a tweaker-looking guy walking around looking into facility vehicle windows. I trained my headlamp on him. He got the message and left.
I am usually not nervous about theft when I am on tour. I employ situational awareness. I am not going to bother locking my bike if I am running into a store for a quick snack in Nowhereville, MT, or even Nowhereville, VT. Burlington, however, is one place I would not leave my bike unlocked unless I could keep my eye on it at all times. Lst year I had a lean-to at North Beach Campground. While I slept, I positioned the bike behind my tent and threaded the cable lock around the frame and front wheel. That is saying something considering I often do not lock my bike when I sleep.