How do you deal with getting a woman's number at a place you frequent when you aren't interested?

For the first time in my 28 years, a random woman, specifically the cashier at the grocery store by my house, gave me her number today (wrote it on the receipt before giving it to me). It's nice but... I'm happily married (I wear my wedding ring and rarely put my hands on my pockets). How do I proceed? Just ignore it happened? Acknowledge it next time I she her and say I'm married? Go to a different grocery store all together? I'm an introvert and an overthinker, but please help.
Edit: This blew up while I was asleep. Thanks for the advice (both serious and not)!
Edit 2: my wife is aware that I got the number. Told her immediately.
If I had the opportunity to tell the cashier "thanks but I'm married" I would have done that at the time. I didn't. So now, my question is "how do I approach the situation when I go back to the store."
Edit 3: I'm not going to text her. Giving my number to random people is not going to happen.


Source.