Is it wrong to sell something that someone has given you for free?

My baby days are done so I had some stuff I didn’t need any more – little sheets, a fleecy cover, it was all nice stuff…. I thought about ebaying it but I didn’t. So I offered it for free on Freecycle to the first person that replied to me – just wanted it out of the little one’s bedroom as well as giving it to someone who might really need it. A few weeks later I was at a car boot sale (yard sale) and saw it all for sale on someone’s stall. I felt furious that I’d given it away and they were selling it. Furious, but I couldn’t quite understand why. Anyway I went up to the woman and told her I didn’t think it was right. Which is not like unconfrontational me. I’ve been thinking about it for about a year now and still feel furious! But there’s fairly big piece of me that thinks that the fury is unjustified. Opinions please!