Perhaps you are thinking of Over the Rainbow in Camano Island, WA (
https://www.overtherainbowfabrics.com/) It is INSANE. They have
31,000+ bolts of fabric....the catch is that the store isn't the easiest to shop through in person - which I guess makes sense since they are primarily an online shop. The bolts of fabrics are literally stacked to the ceiling, very narrow aisles. I was literally on my hands and knees in their attic looking at stuff. I don't know how any non-employee could find anything in there - it's more like a game of chance. BUT their employees know where EVERYTHING is. In fact they specifically ask that if you pull a bolt of fabric and decide you don't want it to NOT put it back were you THINK you got it.
I'm glad I went once but I don't have any desire to go back.
If you decide to go - make sure you confirm their hours. They have limited hours for in person shoppoing