Same thing happened to me yesterday; I saw on the tracking page (and via email) that there was a delivery exception at 1pm. I took the print from the tracking page to the fedex hub at 6pm and the guy handed me my box. Fedex usually runs two rounds, one that ends at 3p and one that ends at 7p. If the first expectation was before 3 and the original claim was "delivery by 3" then that means the box will be back at the hub not much later than 3 (when he gets the next round of boxes.)
It took a LOT of self control but i was a good boy and didnt turn it on until the battery read 100%. Ever since then, it's been gravy!