Turtle Injuries

Question
Turtle: Red Eared Slider.
Habitat: Simple plastic tank, big enough for 2, a few rock's so they can climb up on once in a while. Heating light.
Water & Basking temp.: Water level isn't too high, but enough so they don't get too dry. Basking temp. would be pretty good, I live in California, it's a hot season, so I'm hoping that's a good thing.
Feed: Store bought food, Reptomin Tetra Floating Food Sticks.
Behavior: Acting normal. Nothing strange. floating, swimming around, eating.

I was off at class, and I didn't have enough time to clean my turtles tank, thankfully my grandma did it for me. when I got home she told me one somehow got out and crawled off, but she got it back. I was feeding them when I noticed the smaller one was missing all it's claws on the back right foot, and part of it's tail was gone. I wan't to know if the little guy (or girl?) will be alright, will the tail and claws grow back? I don't think the finger digits themselves are gone, just the claws. he/she can still swim around and eat....I'm just kinda worried.....(sorry I can't provide pictures)

Answer
Your background history is vague rather than providing actual details. If you are going to provide information about water levels, temps, etc...then quantify it, because experts cannot assume you know what "normal", "isn't too high", or "pretty good" is, and we don't know what that means.

I would be skeptical that one just "got out" unless you had water level very near the top and a foothold. It sounds more to me like grandma has a friggin house cat and the story is a bit fishy. It's also possible that if you have an appreciable size differential, that the tank mate bit the toes and tail off. In this case you probably don't have sufficient space for the both of them, and they should be separated. This doesn't explain the "escape" though. If grandma has a predator running around the house, I would advise you to close the room off and use a secure screen lid.

No, the tail will not grow back. If the claws were damaged at the root they probably will not grow back either. The turtle will adapt fine, but infection is a concern, and the primary concern is finding out what really happened and preventing whatever it was from finishing off your turtle the next time.