Don't feel too bad about about taking a fawn, depending on the local recruitment rate, that fawn had somewhere around a 3 in 10 chance of making it through winter, so a manegment perspective it was not that bad of a deer to take regardless of gender.
From a meat perspective it's a good news bad news thing, great eating just not alot of it. When I was new to hunting mule deer on the prairies I shot a few fawns myself, I took a while to learn how to judge an antlerless deer and then I had to learn the disciple to pass on shots unless it really was a "last chance"
What bullet were you using it seems kind of odd for a 308 to perform like that, but true bang flops are rarer than you think. They may drop right there but it can take some time for them to actually expire.