I think I offended someone

I was at the DMV getting my new license and I walked up to the counter and just kind of threw my bag on the counter next to me without thinking because no one was standing there. Then a black lady, about 50 years old, walked up to the counter and about a minute later I realized my bag was in her way so I said "I'm sorry this is in your way. I just throw my stuff everywhere!" And she said "I didn't even see it there. I wasn't going to take it." And she seemed indignant.

I didn't know what to say because I didn't think she'd take it. I just moved it because it was in her way. So I just continued what I was doing and left.

Then it occurred to me that maybe she thought I was racist and stereotyping her as someone who would steal my handbag. I honestly wasn't. I just thought it was rude that I was taking up so much space on the counter.

What should I do in that situation to avoid making people feel like I'm stereotyping them?

Edited: she was definitely not joking. She scowled at me. And I would have done it for anyone. I didn't move it because she was black. I moved it because it was in her way and I thought it was rude.