I have three suggestions...
1) You had previously been featured on the Muppet Mindset. I'm sure representatives of Disney/Muppets Studio check out the major fan sites regularly so someone would have already seen a sampling there - perhaps a follow-up interview where you mention how you've not been successful getting this to Disney might open a door.
2) We have a few "official" artists here on the forum since there are artists who work on Boom's Muppet comics (at least one of which was a member and had posted are before getting the Boom job) - get in contact with them, explain the situation, and see if they might serve as a reference.
3) Instead of sending this to the head of Muppets Studio as an example of your work, why not instead send copies to other creative people in the Muppets Studio (puppeteers, writers, directors, designers) as a gift? At least one of them might then say to Lyelle, "say you know you might want to see this and consider..."