It would not harden in a day in vermiculite I think. Why would it?
From my experiences with egg bound females, I still recommend to just wait patiently, how difficult it might be to do so. As long as she is not lethargic or gets very skinny or anything else changes in a negative way, just try to feed her a small item every couple of days and maybe massage the egg area a bit when you take her out for that. Pushing the egg up and down a bit, as far as possible without using force, might keep it from fusing to the egg tube.
Still, it is hard to make a decision in cases like this, because you never know how things would have went if you took another road. I strongly feel the less bothering the female, the better chances she has to pass it herself. If she is able to, you might keep her from doing it by bothering her. Than you need to interfere after all which is always more risky than the female doing it herself. Of course there is always a chance she suddenly gets worse or dies when you do not do anything, but so far I have not had that happen. The ones that died, I bothered a lot, though one of those had only 2 or 3 eggs left. The ones I did not interfere with, with 2-3 eggs left, eventually all passed the eggs. Only egg boudn females with a lot of eggs are in need of quick help usually.