Alamo 1 dollar charge

When I picked up my car from Alamo on Sunday there was some confusion over an included GPS. Firstly the guy at check in wanted to charge for it. When I explained it was included in price he just said collect when leaving the garage. When I got to the exit at the garage they did not have any so I explained that I didn't need it and it was only on the package because it was a special gold offer and was basically free. So I asked that she just remove the item from the booking so that when I take the car back they won't be expecting me to return a GPS.*
All this is probably not relevant as my question is that on checking my credit card online there is a 1 dollar charge from Alamo and all it says is purchase. Has any one got any idea what this one dollar is for.

I could be a mile off the mark here but I do occasionally see that kind of charge on my credit card bill when the card is used not for immediate payment but purely as a form of card validation by the retailer for a potential future charge. The usual routine is for the charge never to be collected and stay in the "Pending" category on my card account or occasionally just refunded at the conclusion of the transaction so there is no actual debit from the card.

I think you could be correct as it is still showing as pending. I think I am over cautious after the guy tried to charge over 15 dollars a day for GPS that was included in the package.