I have engraved the exact bag from hobby lobby and used the setting of 1000/20. Here are some series on it and photos showing the wash out and what can be done to prevent the washing out:
https://community.glowforge.com/t/washing-engraved-canvas
https://community.glowforge.com/t/glowforging-my-fabric-scraps
I guess it can depend on your definition of washing out. So I guess a more accurate way of saying it is that more than 50% of the design ash will wash off the canvas bag after engraving. That is because the cotton base creates more ash with the laser then a base like polyester.
If you wash your cotton bag without treatment then at least 50% of design ash will wash out, just like it did for you.