Saw my mom's vagina

I don't know if this is the right to place to post this but I wanted to put it here because it's kind of a question just for guys.
My mom always wears a pretty short bath robe around the house after she gets out of the shower, and last night she was wearing it as usual after she got out of the shower. I was in my room and I heard my mom coming out of the bathroom so I started to walk out of my room to go use the bathroom. We have a rug in the hallway right outside of the bathroom that always gets crooked and out of place so it always has to be adjusted. So I was walking out of my room and I saw my mom in the hallway and she bent over to adjust the rug because it was crooked. When she bent over her robe rode up and I got a full view of her butt and vagina. I just sort of stood in my doorway and watched her do it and when she was done I just kind of went back into my room. She didn't notice I saw her at all.
The thing is, I kind of liked it. I can't stop thinking about it now and I don't know if it's ok or not. I've always thought my mom was pretty attractive and all my friends talk about how they think she's hot. Is it ok that I think of my mom in that kind of way? Has anyone else ever had something like this happen?