Understandable. Civics are quite well made, so I wouldn’t expect it to immediately become a rust trap from some short term splashes. Generally, mechanics will tell you other stuff is wrong, but it only matters if it’s adjacent to what they’re working on for liability. They may find some problems like a glazed dipstick from going too long between changes, but it’s just informational.

If you’re interested in putting that plate back on, my guess is that they used plastic zip ties on a metal shield. Usually, manufacturers will only use more expensive metal guards if it gets hot in that location. You can buy metal cable ties real cheap that will hold up much better. Fasteners are also cheap if you can figure out which one, but I dunno if I’d bother on a car that’s on its way out in my mind.

Recommendation is just to prioritize it before Winter weather.

Sorry your money situation is so dire. Credit can be the hell that keeps on giving.