Do females ever have plugs when popping?
No. That would be a male.

Adults are very hard to pop. They have strong muscle control. Seeing plugs though guarentees it's a male.

I bought an adult female a few years back. When she arrived, the body shape and size just didn't "look" right for an adult female. I probed her and the probe went deep and came out with a plug on it. Sure enough, it was a male.