Drain pipe in the basement - rats?

Hello!

I don’t know if this is the right category, but I couldn’t find a more suitable one.
We have completely renovated a 60-year-old house.
The plumbing company installed a provisional "worker’s toilet" in the basement. Next to it is a branch of the new drainpipe where presumably the cover flap was forgotten. Because the room suddenly started to smell so bad, we sealed the hole with tape. Earlier, my husband noticed some movement in the basement on the other side of the drainpipe (the wall where the pipe runs through is broken through to the adjacent room). When we checked, we found that the tape had signs of gnawing and had come off.
Well. Now we are (especially ME) desperate: how likely is it that we now have the creatures in our own four walls? We assume rats, although we (so far) have not found any droppings. We have now covered the pipe with a lid (commercially available) and dismantled the toilet. We have also set up a rat trap. Is it true that rats keep coming back once they have been there? I am exhausted, terrible years of renovation are behind us and now this…!!! Who can help me? With tips, comfort, or anything else… what should we do now? Is the plumbing company to blame? They should not have left the pipe open!!!!
I am grateful for anything! Please.

I wouldn’t panic just yet. You have now closed everything up and taken everything down, and if the rats (if they are indeed rats) can’t get in anymore, they might look for another home. In any case, it is right to react quickly and decisively before the problem becomes established. Make sure to seal everything where they could theoretically get in and be careful not to provide them with any food sources.

Friends had mice in their apartment a few years ago, but that problem was actually solved quickly. They live very rurally and had too much food left out with the patio door open at the same time.

Hello Winniefred! Thank you very much for your response! I am really feeling bad, I am very afraid to go down to the basement and experience a nasty surprise there. But there is no helping it, we have to face the whole thing now. My husband is currently contacting a sewer worker company (we had them here before when they recoated the drainpipe inside). I am so exhausted. We NEVER pour food leftovers into the toilet, I am totally at my wit's end. We will now seal the pipes with concrete or have old blind-ending pipes milled off. The sewer worker said that the rats probably won't come anymore once they realize the opening is now closed. They would look for easier paths. We were rather advised against rat funnels or rat flaps in the pipe.

Rats, if they are any, are unfortunately clever animals and like to come back. Set up an IR camera and record. Then you will also know if they are really rats.