I think my cat is dead? :(?

We have a cat. She got a wound on her upper thy/ butt area. She has gotten this before and we took her to the vet, and they said she just got snagged by something like a twig and then bacteria started to eat at the skin causing a hole. So this time we didnt think much of it, my mom was going to get her some echinacia but hasnt been able to yet. Lately she has been disappearing outside for a whole night, then shed come back in the morning to eat and then disappear till the next morning. But this time, she didnt come back for breakfast in the morning. I feel terrible. I get the feeling she went off to die somewhere and I just want her to come back :( I think we should have done something but last time this happened the vet said there wasnt anything we could do but give her echinacia, and we werent able to do that right away. What do you think happened? Do you think she might be dead? :'(