I don't think she does, but I seem to be in the minority.
We see her lose the blade when she battles David. After Joel finds her, we see them leave right away, without scavenging the place. Are we to assume they got outta there, found no one else in the area so then went back in? I just assumed they left and thus, bye bye switchblade. Maybe it's one of those "video game" things we just accept... like, how can she possibly have her backpack in the last scene too? Joel didn't carry it out, and I can't imagine he'd leave Ellie unconscious in the car to go back in there and look for it.
I could pay more attention next time I play the Spring season... but if I'm not lucky enough to get that glitch in the tunnel, I'm too busy getting my butt kicked to pay attention to what Ellie's doing. I suppose I could wade through a bunch of play-through videos online and see if I notice her using it ever... but I'm not THAT curious, I can't imagine taking the time to do that.
What say ye?