I think retirement is a pipe dream...

Ok don't quote me on that. I am pretty sure it was a 401k but it is possible it was some other kind of account.

The one with my mother was definitely a 401k.
Gotcha -- basically, any personal 401k contributions cannot be kept from heirs/beneficiaries (although there certainly may be tax issues involved depending on how it is invested). As for company/matching contributions, that's a different ballgame. I'm far from an expert, but there is no way that a company can keep private 401k contributions.

As someone else mentioned, it might be some kind of annuity product and, if a survivor benefit isn't set up the right way (basically, the product would then cost a lot more) then, yes, that could be kept by the company. Again, that would have made the product a lot cheaper for your dad.

As for your mom's story, very sorry to hear that. That's why I cashed out my retirement when I retired, and invested it myself.