No it's clearly been developed OK, you can see "400TX" in the edges. I agree with the crinkling theory because the densest stress-fog lines are at the corners of the sprockets, which means the film has had some seriously tight bending applied to it.
Note that you can get stress fog without the film looking crinkled. Just bend the film real tight and release it; the backing won't show a fold but the emulsion will be fogged there.
If that's the case, perhaps the students tried to rewind the film into the cassette without releasing the rewind button (assuming an all- manual camera), over-tightening it. I've never had this problem either - very odd!
Cheers,
kevs

