I may be fine then, but was the paint scraped off of the frame hanger before, or after you cut the bolt off? In some cases, just the thickness of a big nut will hit the frame there, so it made me wonder about that obvious scraping.
If it was done prior to you cutting (or done by the tool when you were cutting
) then you may be good.
If you're only 99% sure, then the next time you have a chance, have someone jump up and down on the bumper/tailgate while you watch the shackle cycling.
Paul