Dear Mike
A quick check with Liquitex's website indicates that their "Soluvar" varnish (I assume that is the one you used but they do have a range of them) is probably a "soft" varnish and/or a Low Molecular Weight resin because it is supposed to be "self-levelling" and "removable" (something akin to Damar I guess). Most importantly, though, they stress in a couple of places NOT to use Odorless mineral spirits to remove it or to thin it, only regular Mineral Spirits or turpentine are to be used. (Odorless is maybe not quite strong enough? I don't know.) Anyway, I thought I should let you know. Here's the link:
http://www.liquitex.com/products/varsoluvargloss.cfm
Considering its purported self-levelling qualities, I would not expect that overlapping the hole will be a problem, especially since you said there is only one coat of varnish. Maybe after you patch the hole and after that has dried sufficiently, you might want to give the entire painting another layer? This may even everything out sufficiently to eliminate any lingering evidence of the hole.
I am as surprised to read as you must have been to see that the sugar mixture took the varnish off. Maybe run that one by Liquitex.
Best luck.
Juan