There was no Creature Shop involvement (the McDonalds food puppets were made by other companies). Hardin said she planned to explain more about that meeting in a future article, but didn't. We'd have to try to contact her (she's on Facebook). Speculation, it may have simply had to do with what sound stages were being used where, meaning Jim Henson was in the vicinity and wandered by, or was deliberately scouting talent. That sort of thing (meeting someone notable because they were doing something in the stage or recording studio next door) is not uncommon.