And why wouldn’t security grab you and question you? They may have Barney Fifed it a bit, but they are responsible to make sure that a person with a grudge (which would be you) doesn’t get too near and go for assassination. Trump is especially despised, but security works like that for all Presidents.
So they questioned you and released you back into the wild — about what you had expected actually. They made some inquiries about you. You didn’t expect that?
A bit of unfriendly advice: if you’re going to play around with civil disobedience, you need to make contingency plans about jail. Mohandas Gandhi, the Rev. Martin Luther King, Rosa Parks, the Freedom Riders, and those who desegregated lunch counters didn’t make their actions all about themselves, and they took real risks. You might learn from them.