I accidently flat out ignored my coworker today as she "bye, it was nice seeing you" and feel really bad about it lol

We work retail together and don't really talk much, but the few interactions we have are friendly enough. She doesn't work there that often, only like around once a week.

While I was plugging in my work IPod to leave I was a little overwhelmed from everything that happened that day, and said "see ya" to her in kind of a flat tone. She responded with "See ya, it was nice seeing you again." I looked at her when she said that, my brain kind of froze, I just stood there awkwardly looking down without saying a word for like 5 seconds, and then I just left without saying anything.

I know this probably sounds like nothing, but if my brain freezes and I come across as cold/dismissive to someone it bothers me lol. Hopefully she just took it as an awkward moment or something and didn't take it badly.

I don't work with her again for at least another 2 weeks, and there's nothing I can really do about it now. It is what it is I guess.