This is an interesting question, so I did some research. And here is what I found...
from
http://www.baseball-reference.com/bullpen/Save"Blown Save
A blown save (abbreviated BS) is charged to a pitcher who enters a game in a save situation but allows the tying run to score. Blown saves were introduced in 1988, but are not an officially recognized statistic although many sources keep track of them. Once a pitcher blows a save, he is no longer eligible to earn a save in that game (since the lead that he was trying to "save" has disappeared) although he can earn a win if his team regains the lead."
What I've done for our team in the past is credit the relief pitcher with the inning or 1/3 of an inning(if/when an out is finally recorded), but not the 2 runs that scored, since those runners belong to pitcher that started the inning. He wouldn't get the Blown Save either because the new pitcher got the batter to hit a ground ball in the infield which is what relievers are typically asked to do.
The pitcher can't play all of the positions in the infield (even though some would like to).
I checked with a friend who was an official MLB scorer and he confirmed that no Blown Save would be awarded due to the error.