I'm wondering if Municitions Failsafe would work for Bombs that don't hit.

No. Upgrade cards that have the "Attack:" heading are secondary weapons. Bombs do not so they are not secondary weapons.

It's in the core rule book p19.

It is also specifically spelled out somewhere that bombs are not secondary weapons. So yeah, what smuggler said. (I think it's in the FAQ)

That said, they could conceivably print a bomb in the future that was a secondary weapon. I doubt they'll do it, but the rules don't prohibit bombs from being secondary weapons per se.

but the rules don't prohibit bombs from being secondary weapons per se.

They do

"Bomb Tokens do not count as obstacles, and bomb Upgrade cards do not count as secondary weapons"

From the "Using Bombs" reference card

I stand by the idea that that could conceivably change in the future (though I don't think it's likely to) and that that part of the card is to preempt the relatively common question about whether bombs count as secondary weapons. Completely academic question though. No current bombs are secondary weapons with or without that line on the bomb reference card.