UMs: Lost treasure part 3

So this weeks edition of lost treasure really has a kind of arthouse vibe going on, but still big mysteries none the less. So slap on that great theme tune version and peruse the following:

The Isabella Gardner Museum Heist is famous for not only what was stolen, but by how incompetent just about everyone involved on both sides were, yet the thieves still got away with it:
https://www.reddit.com/r/UnresolvedMysteries/comments/p1wn5f/lets_talk_about_the_isabella_gardner_museum_heist/

One of the largest art heists in history was perpetrated in East Germany back in the height of the cold war, in 1979, which makes it even more impressive/baffling that it hasn't been solved:
https://www.reddit.com/r/UnresolvedMysteries/comments/l3nzkj/it_was_one_of_europes_biggest_art_heists_yet/

A old B-25 that crashed in the 50s wouldn't really bat much of an eye by itself, but there are some wild theories as to what it was actually carrying that day and why it may have been a secret:
https://www.reddit.com/r/UnresolvedMysteries/comments/kruyid/a_mitchell_b25_bomber_that_crashed_and_sank_into/

Kind of a different tale. An old couple that were school teachers die in 2007, but leave behind a painting in their bedroom worth over 160 million that was reported stolen in 1985 from the University of Arizona Museum of Art in Tucson. Were they the culprits, or just unwitting participants?
https://www.reddit.com/r/UnresolvedMysteries/comments/949squ/a_smalltown_couple_left_behind_a_stolen_painting/