That is a good ending to your story, I'm sure there was some surprise when you saw some thing pop out of the substrate. :woohoo:
I have also notice, as long as the spider has a burrow and it is closed off the crickets tend to leave the spider alone, it is when you have the spider and the cricket out in the open is when things goes wrong.
I give my smaller spider larger crickets, Especially my pokie slings.
I started feeding my B. vagans medium to extra large crickets when they wore 4 to 5cm same with my C. cyaneopubescens he gets medium to large crickets.
I only really feed the more aggressive spider that I know that does not play with there food!
I just make sure they take the crickets then and there or as soon as it hits the substrate, if I see the spider is not interested in the prey item right away I squish it's head.
What I do find with feeding B. vagans like this is. They are allot bigger know much bigger than the Extra large crickets, and on the odd occasion I have to give them medium crickets and they still attack the cricket with the same aggression and drive that they attack the adult crickets with, where the other spider that get prey items smaller tend to nicely pick it up and inject it once or twice and take it easy in the whole catching of the prey items, more relaxed.