1998 Mercury Sable Compression test

I want to see if you understand exactly what happened. My girl was driving and ran over a truck tread which caused my lower hose to break stupid me left the plastic cover off. Wel when the car did this she pulled over the side the gauge never went to hot but as she was stopping the car died. I tried to start when she was towed home and wouldn't start and felt like no compression at all. I found a bad head gasket and changed it but didn't have the head surfaced. But compression is still the same. I don't have a compressor so a leak down is out of the question. I have a compression tester and have already gave the dry lbs earlier. I fear a valve problem but cant be sure until I do a wet test is there any other area I have missed that you know of.