I rescued a baby Mohave Ground Squirrel from my cat.?

They're listed as a protected species. Its not bleeding at all, but I think it might be too young to be have weaned. I know its mother will never take it back since I touched it. I did some calling and I found a place that will take it and try to save it, but I can't get it there right now. Is there anything I can do to keep it alive until I can? Its in a shoebox with a dry washcloth and I put a piece of lettuce in there, but I don't think it can eat it yet. I have baby formula here and human breast milk. Would it be able to drink that? I'm sure it probably couldn't tolerate cow's milk.