I was in the Army stationed in Oahu in the early 90s. We accidentally brought back some ants from training in Arkansas
What do you think caused you to return with ants?
I think they just hijacked themselves in our gear.
Accidents like bringing ants back from a trip with you can happen. It's important that you contact someone when that happens, especially if it is an invasive species.
Thanks,  that's what I did once I realized what happened.
Great! Because some plants are not compatible with foreign insects. They can destroy the local flora and fauna, so it's best to contact the authorities.