The Carbona Stain Devils work really well. Here is the link for the rust one.

https://www.amazon.com/Carbona-Stain-Devils-Rust-Perspiration/dp/B001VNV9KA/ref=sr_1_1_a_it?ie=UTF8&qid=1505616574&sr=8-1&keywords=carbona+stain+devils+rust+and+perspiration

Just for a second opinion, you might ask on the quilting forum.

I would try lemon juice and then lay it in the sun....some say sprinkle the stain with salt and then add lemon adn sunshine..
May not completely remove it but will certainly lessen it and it's a gentle remedy unlike Whink or another compound containing oxalic acid.

Thanks @lindac92 I found your post and it helped me out. :)

Did you get rid of the stain? Sometimes the "old wives" knew what they were doing.