Good Deed FAIL

There are many occasions when I make a trip to Costco and while loading a lot of things I didn't need to get into the back of my van (oh yeah, and the couple of things I went in there for) and getting all the kids buckled someone will offer to take my cart for me while they return their own, or because they are on their way in. I've always found this to be so incredibly nice. So I made a goal to try to do this for someone else. I was feeling particularly outgoing one day a couple of weeks ago so I decided today was the day! The day I was going to "pass it on"!
I found my parking spot, it happened to be pretty far back in the parking lot. (when is it not anymore, lately?) I started to unload my herd of children and noticed a man with a cart walking toward the cart return a couple spaces closer to the store then I parked. I stopped him and said, "Here, let me take that!" with a great big "aren't I a good citizen" smile on my face. To which he replied, "Huh?" (pause pause) "Oh, ... uh..."
Then it hit me!!! HE WAS JUST ON HIS WAY IN THE STORE!! Totally mortified I said "Oh my HECK!! You're just going in aren't you!?" He said, "Um, yeah." Then he noticed my herd. So then he continued with, "But, here you go. I'll let you have this one and I'll just get another."
By this point I wanted a hole to crawl in. I refused his offer and told him "sorry", because I felt like I needed to apologize for inflicting my ditziness on him. Then I said a little prayer that I wouldn't run into him in the store.
I think it all comes down to my choice in words. "Here, let me take that!" Couldn't I have just thought to say something like "..." oh my heck I don't know what to say!! I think I need to find a different good deed that I can handle a little better!
So there you have it folks!!! My Good Deed FAIL!!!