TexasCHLforum.com

When the employee touched you (somewhat inappropriately I might add) look at them and say, "I am Borg...prepare to be assimilated."

I'm sure that no where in Costco's membership policy does it say that it gives their employees the right to covertly frisk you.
Could this fall under Texas Penal Code Chapter 22.01?

Sec. 22.01. ASSAULT. (a) A person commits an offense if the
person:
(3) intentionally or knowingly causes physical contact with
another when the person knows or should reasonably believe that the
other will regard the contact as offensive or provocative.

If a store employee just walks up to me and starts touching me I'm going to consider it offensive and provocative.

I agree with others who said don't admit you are carrying a weapon unless asked by a peace officer.