Well, I wrote Ranger Don Pfanz at Fredericksburg and asked him about that passage about Hooker at Chancellorsville.
I'm inclined to be skeptical of the bugler. First, it not contemporary and if there are plenty of eye witness accounts of Hooker's injury, especially letters written after the battle or journal/diary entries, I'd put my money on those first. The bugler may have been a disgruntled individual who was disparaging Fighting Joe. BTW, I found the tidbit on page 83 of History of the 121st New York State Infantry by Issac Best.
Here's what Ranger Pfanz wrote back:
This is an interesting account, but I don't put much credit in it for three
1. I don't believe army commanders had their own buglers. What
would they have used them for?
2. Second-hand accounts from anonymous sources are usually wrong.
3. We have numerous accounts of Hooker's wounding plus several good
accounts by those who were close to Hooker, but not friendly towards him,
that insist that he did not drink during the battle.
Still, I appreciate you passing along this account.
So, there we have it. A disgruntled man who wanted to disparage his old commander.