This isn't a question to start a fight or anything just curious as to your opinions on the matter...

During black Saturday we had an individual who was dress like a woman but was apparent was a guy who was shopping in the women's department. Well once this person had gathered a good number of attire then went into the little boys changing room to, was thought, to try on the clothing. Security didn't know that to do as they didn't want to offend a potential Transgender and possibly get slapped with a lawsuit. Well after the person left security inspected the room and it looked like they had peed themselves.

Only to find out later that it wasn't pee. So my question is, What rights did security have in this instance to protect the rights of TGs but also protect everyone else from, might have been, a potential sex offender?

I used to work loss prevention/security, and let me tell you at least for the company I worked for, preventing a lawsuit was by far their second most important thought when deciding "what to do" (safety came first).  For us, when in doubt (for an issue like this), observe and see what progresses.  If it looked to be possible criminal activity that was theft-irrelevant, we'd either call law enforcement and let them do what they felt was necessary or make our presence known to the person in an attempt to deter.  Regardless, we were not permitted to accuse of anything.

have a salesperson/security hovering outside the chaging room and keeping asking  'is size right, what fits' in order to let the person know they have to quickly try on and buy or leave.