Oh, yeah, you can easily ding packs, including hard cases. And the damage doesn't always show. If you smell it, you know a cell leaked.
Typically, a contaminated cell will die sooner, usually puffing some first then croaking. So the probability is that somehow he did ding a cell.
Re 18650's, I'd love to see cells for sale in various parallel configurations spot welded, including the insulator under the positive side nickel strips. So you'd just buy 5p or 10p, whatever, in modules ready for use just like single cells of 5 ah, 10 ah, etc. Then the DIY crowd need only solder to a few strips to make the series connections.
RC packs, of 4s or 5s 2p etc would work too. We'd handle them exactly as we do lipo now, without as much need for the fire box storage area.
Or similarly, 13 or 14s 1 p strings. Either way, you'd have that modular convenience to run a 5 ah pack one day, a 40 ah another.