How do I know if my frame is bent?

Back in december 2011 I was involved in an accident with a deer and it tore my right fender off and damaged my bumper and my insurance which is allstate totalled my car due to to much cost to repair the damage on my car that my only transpiortatiobn so they asked if I wanted to keep the car I said yes so they issued me a 1300 dollar check in the mail which was great but I just replace my tires last month and I asked the mechanic will my car pass state inspection in may with my fender off they said no it wont which is fine im not mad about that cause I wanted body work done before then but I had a friend that works with me look at my car of course it was night time he didnt thoughouly look at my car but he said it looks like my frame is bent I told my dad about it and he said if your frame was bent your insurance wouldnt have sold you your car back cuz they would say its not safe to drive is that true that they never would have sold my car to me back how can I tell visually if my car frame is bent the only thing I notice is that I have a tiny dent in it in a couple of weeks im going to go drive around and get a estimate on body work for my car so I can get a price range but when I had my car towed to firestone and they replaced my tire wouldnt they have noticed that my frame is bent and if they did wouldnt they tell me right there the only thing they told me was that I have to replace all my tires they said it was showing steel which was fine I replaced it last thing I need is to have a blow out when driving