This just happened again, thought I would document it here. The instructor had a webwork set of 50 problems which they opened to students, then only later noticed the path names were missing for all 50 problems. They had to reconstruct the homework set, but otherwise no serious problems.
The instructor reported some internet issues while they were working on it: When asked if they had used back buttons or a lot of windows open this was the response, "I do typically have a couple of windows open, and I definitely could have used the back button at some point. My computer also tends to randomly disconnect from my home internet, and I'm sure it happened at more than one point while I was working yesterday, so I'm sure that couldn't have helped."