Two things, one more known than the other.
1. You can't get Covid just by touching something contaminated. It has to enter your body through an opening. So, if you have a bag and need to get something out of it, keep sanitizer handy, and sanitize your hands after going into the bag and befure using what you grabbed.
2. Less unknown is how much the virus can be transferred through physical contact. First, you would have needed someone to cough/sneeze directly onto their belongings. If security were to touch this, say even 30 minutes later, how much of that viral load is being transferred? It is not going to be 100%. Then if they touch something else, it would be less 100% of that last amount that transferred. How much of that is required to actually get you sick?
Think of the same concept as going grocery shopping, and touching stuff that others have touched. If it were such a big issue, there would be large outbreaks with grocery stores being the epicenter. We aren't seeing that. I'd be more concerned with needing to be face to face with security while they check.