how to not seem like a loser

[Degenerasian]

I agree with what you said, DO NOT apologize to a girl ever (unless for obvious reasons). I think you're in a tough situation here. Depending on how long it was since she left you that message - if over a month, then you can just forget about it. If it was less than that, you have a shot, so call her up and ask her to hang out, get a coffee, or whatever.