Congratulations on your awesome find! That's why I love estate sales - those occasional treasures make it worth going through dreck. I've been in the thrift shops a couple times and never found anything interesting.
My best quilting find EVER was at an estate sale. Last hour, last day of a 4-day sale. The place was mostly cleaned out, and the estate sale people were starting to move the leftovers into one room to haul off to wherever they take unsold stuff.
I stumbled onto a stack of quilting books in an upstairs bedroom. Then another stack. And another. I started going through everything when the estate sale manager came in and told me she needed to get things out of the house and to just take everything - there wasn't time to go through it all. I told her I wasn't sure I wanted to pay for a bunch of stuff I might not want. She said she'd sell me everything for $40. We boxed up all the books and magazines. Unfortunately, if a fabric stash had been part of the estate sale, there was no sign of it at this point.
Included in the lot was over 80 quilting books and over 150 vintage quilting magazines and newsletters. It was an instant quilting library for $40. I sold the books that were duplicates of what I already had and made more than my $40 investment. It was a windfall of epic proportions!