Paying vendors in cash...

I paid for my dress in cash this morning and when my dad found out he shook his head at me like I did something wrong.
He said you should always pay with a check so you have the canceled check as proof that you paid. I got a receipt with a letter head and both her and my signature at the bottom. Shouldn't that be enough? By paying in cash I avoided paying tax. I gave my florist cash for the same reason...and planned on giving the photog cash.

Now he has me worried....about that and about whether or not I will get the right dress. I'm getting it from Phyllis at gownfind, and since there are no pictures online, I had to go by style # only (I got the style # off the tag at Lillette's). I described the dress, but it won't do much good because the designer won't release pictures of the 'limited edition' dresses.

Am I crazy for doing this to save a few hundred bucks (more than a few actually- the dress went from over budget to under budget)?

My dad just totally rained on my parade...I know he's just trying to look out for me...but now I feel like throwing up.

Any thoughts?