Can it be this one? Found it on the postsecret site under "how do i mail in my secret".

PostSecret
13345 Copper Ridge Rd
Germantown,Maryland
20874

sweet, i will definetaly send some in.

I actually think

PostSecret
13345 Copper Ridge Rd
Germantown,Maryland
20874
(The adress i replied) is Frank's home adress.

oh cool...so is that right??

Think so. In a interview found on links(Milwaukee Journal Sentinal: Postsecrets ) on this spot it says;

"Warren won't mind that I'm giving you his home address. It's on the cover of his first book: 13345 Copper Ridge Road, Germantown, MD 20874. About 1,000 postcards a week show up in his mailbox."