It's Boston Marathon right to make or not make an offer to any athlete American or not. Now that Mebrahtom see that they passed on him he have several options and the best two being:
continue preparing to run a spring marathon and go to a very fast course and get the 2:06:55-2:07:30 he know he is still capable of running. Send a message to Boston they made a mistake!
use the time to focus on regaining his track speed and go for the U.S team for the World 10000m. This would be his best bet as it would be a springboard for fall marathon training.