So, right off the bat, the problem with ocd that involves these types of questions is that the reassurance you seek is the compulsion to your obsession. Our reassuring you, all your research, etc. is going to keep you stuck in the ocd rut. I want you to know that. The only way to recover from ocd is to stop the compulsion. Live with the worry and thought like any other thought you have a million times a day. And THEN there is a chance it gets dismissed. OUR answering it solidifies it in your anxious brain as a realistic thing for you worry about and the thought gets stuck. Do you understand that dynamic? Every tie you try to reassure yourself and receive false reassurance, you are prolonging and worsening your ocd.
Sigh, I hate to even do this and hope you get help with your ocd (try ERP therapy, online or with a therapist). Bats roost in colonies and their droppings accumulate in mass and are not something you wouldn't see. You would notice signs of a bat infestation. And you would notice if anything else happened. This sounds inordinately irrational and part of your ocd. Get some therapy to feel better. OCD is one of the most disturbing in terms of how patients feel anxiety diagnosis but the one that people get the MOST relief when treated. good luck