I stupidly forgot to pour out all my extra melted isomalt onto a mat, and now I have an inch of hardened isomalt in the bottom of my pyrex jug. Is there any way to get it out, or should I just toss it, and go buy a new pyrex jug before hubby gets home??

Have you tried microwaving it?  If it doesn't wotk, nothing is lost by trying.

You have many options to save it.  Microwave should work.  The two enemies of sugar are water and heat.  If the microwave does not work, then either running hot water or if there is room, pouring boiling hot water into the jug will work.  May take a few treatments or some time.  Also, if your oven goes low enough and the Pyrex is rated for a high enough temp, putting it in a 200 F oven for about 10-20 minutes should work.  But microwave and boiling/how water should work fine.

Yep, just plain boiling water will do the trick, add water, let soak, stir and empty. Repeat until it is all clean :-) 

I am always amazed when I read reviews of a sugar based recipe (hard candy etc) and people whinge about having to throw stuff away as the sugar stuck all over it and 'ruined it'  when hot water will melt it all away.