I'll second the comment that the employers' real problem is not the bicycle commuting, it's quitting to go on vacation.
For jobs over a certain level, prospective employers will ask why you left previous jobs, and about gaps in employment. As noted, if you did not return to your previous employer after your tour, you need an explanation of why you quit that convinces a new employer you won't leave them soon. (Even if you were about to be let go anyways, you'd want some public reason for changing jobs).
How you get to work shouldn't be an issue at all, unless the company expects you to use your own vehicle for work (delivery, etc.). Given the other workers taking trains and buses, this doesn't sound like the case.
Since most employers (at least outside MN) only know bicycling is weird and dangerous, they won't believe the bicycle is more reliable and leaves you energetic until you show them (i.e. after you've been hired). Just stick to work related issues - you're reliable, on time, and show them you're energetic without trying to educate people that don't know you about issues they don't need to care about.