What if I don’t get a second shot

I work as a plumber and was sent to another business to do work. I caught eyes with another person more than a handful of times and it was held. I was mesmerized. Was able to make very light conversation at the end of the job but shes on the clock and so am I, also doesnt not feel professional to be flirting on the clock. Problem is its not a business id ecer go to in my free time nor would I be allowed due to building security. Im punching myself for not engaging more but the time did not feel right, what should I do? Or do I let it go.