Failing to properly close a quick release is certainly foreseeable. It is not an uncommon thing to happen. The user is expected to loosen and tighten that quick release as part of the normal operation of the bike, when fixing flats, using bike racks, etc so there are many opportunities to have a problem.
"Foreseeable misuse" Here's a good question for all you shop mechanics: "What percentage of quick releases do you estimate are improperly used?" My personal guess is at LEAST 25%. That's a lot of foreseeable misuse. Once the wheel is out of the dropout, it's anybody's guess how it got there.
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My greatest fear is all of my kids standing around my coffin and talking about "how sensible" dad was.