I heard a similar story the other day by a friend of mine about his colleague. This guy left his job at previous company while his Green Card application was in the 2nd stage. He was tired of waiting in that 2nd stage for years with the hope of reaching to final stage. Finally he got too tired, and he switched the job to a different company. Just within 1 week of joining a new company, magically USCIS released new dates and that guy's application was able to go in the final stage of the Green Card process. Unfortunately, for that to happen, he needed to work with his previous company. He has no option than to talk to his old employer. They took him back.

Weird things happen with immigration cases. And big corporates are sensible enough to understand such situation and help good employees.