Scott.
Their metabolic rate is very fast, not as fast as humming birds, but fast just the same. The frightened state of the bird was probably burning up what it was consuming while your wife was holding it. So, you may be right that the flight to the roof sealed it's own fate. But hey, it's a wild bird and it's just following it's natural survival instinct to get away from what it thought was danger. Don't take it too bad, you did all you could do with the short time you had to do anything with.
I applaud you and your wife for your efforts! There are way too many people out there that will just, run over the turtle trying to cross the road; I'm glad you guys are not one of those people!