That's a good point... but this ".gov" website says that the House would have to choose between the top three candidates,
https://www.archives.gov/federal-register/electoral-college/faq.html. So the third option would just have to win a single state in order to be considered. The third place finisher would likely be Bernie, though, in that scenario. But I could totally see someone like Romney or Gary Johnson winning one or two states.
Do we have to go back to Teddy Roosevelt to find an election where the third place candidate even won a single state? I checked, and neither Ross Perot in the '90s or Anderson in the '70s won any states. That's as many third party/independent candidates as I can think of that got substantial votes, since the days of the Bull Moose party. And here we're considering a scenario where not only the third place but also the fourth place finisher would get some electoral votes.
Probably won't happen, but like you said this is a crazy year.