Take it as a lesson or fight it?

I rented a dress for a wedding for $70. I got a dress in person that I like instead so I canceled the rented one. I didn’t realize that since it was within 30 days it now goes towards a credit on their website, I don’t get it back. I didn’t realize this like a dummy and have been waiting for a refund to my card. I checked today on their website and found this out. I don’t think I’ll ever use that credit so I basically lost $70. I was sick the week prior to canceling that would’ve been before 30 days, so do u guys think I could fight this or should I just take the L?