I found a corroded drain hidden in a basement bedroom

[Mariah Porter]

I've been having some mysterious water issues and my carpet got flooded in the dead of winter the other day. It seemed very strange because I did a test with a pressure gauge and there was no plumbing leak, and the ground is very, very frozen outside so it shouldn't be seepage from outside. I pulled up my carpet and pad and found a weird cement patch that had been poured over a low area in the slab. The patch was all broken up because the water had weakened it. I pulled up a big chunk and found this corroded drain. I've attached a picture. Seems a little shady to me that it was badly covered up. Is this something that the sellers should have disclosed? I know that they bought the house as a flip and finished the basement. I've had several other major problems and I'm feeling like the sellers should have known about some of them. I've been renting out my extra rooms and have had tenants displaced a few times because of random things like this. I've lost a lot of money in vacancy and repairs.

What would you do if this had happened to you?