Vinegar works only on the old-fashioned organic dyes (made from organic materials such as onion skins, etc.). Almost all commercial dyes these days are chemical in origin, so vinegar is unlikely to help.
I would still wash the quilt with Synthrapol in a large washer, even if you don't use hot water with it. Do *not* wash a finished quilt in Retayne as it will permanently set any bleeds.
Sounds like this fabric has a crocking issue (dye transfers during mechanical rubbing even when dry) but not a bleeding problem. Another thing you might want to consider doing is pinning an old white sheet to each side of the quilt before putting it into the washing machine. That way if there is any crocking of dye in the wash, it will be onto the sheets rather than the rest of the quilt.