Is Gilbert Guerrero a 2500 US player? According to the FIDE website, Gilbert Guerrero is from the US federation and 2500 Elo. I have never heard of this player, who mates GM Campora in ... 11 moves! 

Here is the game from Chessgames.com

[Title "Gilbert Guerrero vs Daniel Hugo Campora, Lima 1999"]
[FEN ""]

1.e4 Nf6 2.e5 Nd5 3.Bc4 e6 4.d4 Nc6 5.Nf3 Be7 6.O-O O-O 7.Bd3 d6 8.Qe2 dxe5 9.Qe4?? (9.dxe5+=) Nf6?? (9...f5!-+ 10.Qe2 e4) 10.Qh4 Nd7?? (10...exd4! 11. Bg5 g6-+) 11.Qxh7#1-0



Could we assume that Gilberto Guerrero is actually Hernandez Guerrero, Gilberto? Here is his Wikipedia page.
Did Hernandez Guerrero, Gilberto ever play for the US?
Has the game been played in classical time control? This game looks like a joke!
Could we assume that Gilberto Guerrero is actually Hernandez Guerrero,
  Gilberto?


We could but we would very likely be wrong.

First a word on how FIDE allocates FIDE numbers. FIDE doesn't allocate individual numbers to players. Instead it allocates ranges of numbers to individual federations. 

Gilbert Guerrero's FIDE number is 2012707 and was allocated by the US federation.
Gilberto Hernandez Guerrero's FIDE number is 5100011 and was allocated by the Mexico federation.

For that to happen the same player would need to have registered with each federation resulting in one player with two FINs. Now that did happen in the early days and so is a possibility but is unlikely.

According to his Olimpbase records Gilbert Guerrero's only FIDE rated games were 12 games played in the second half of 1996 which gave him a rating of 2500. 

Checking the Olimpbase data for 1997 for other players called Guerrero we see only one other, a Spanish player called Manuel Gomez Guerrero. He also has FIN 2207893, which is different from Gilberto Hernandez Guerrero, who has FIN 5100011, so not the same player.

The next step is to find, from Gilberto Hernandez Guerrero's FIDE profile what the details are for his earliest recorded result in FIDE's published data. To do that, in his profile, click on "Click to view All previous periods" under "Individual Calculations". There scroll to the bottom to see that there is an entry for July 2001. Clicking on that we see that the entry is for "Hernandez, Gilberto".

There are two possibilities here.


He changed his name some time since 2001
There are two players with different names but the Mexican federation re-used the FIN when one of the players died. By the way, the English Chess Federation did this with Tony Miles' FIN when he died! So, it can happen even with great players.


OK, back to the Olimpbase files to check on Hernandez, Gilberto. The Olimpbase records for this player go back to 1987 and the FIN is 5100011, the same as Gilberto Hernandez Guerrero.

Are Gilberto Hernandez Guerrero and Gilberto Hernandez the same player? Probably. They are the same federation. Maybe he did change or correct his name just before July 2006. The ratings match up before and after with no big jump. Furthermore it is very unlikely that a GM had a change of FIN like that in 2006. 

Regarding the Campora game, here are his olimpbase records. He was 2543 in the July 1999 list and 2534 in the Jan 2000 list. Even playing blitz blindfold and drunk he would not have made those moves.

Apropos the reuse of Tony Miles' FIN. From his Olimpbase records you can see that his FIN was 403385. Today the player with that FIN is Andrew F Footner. Check his rating history and see that apparently he had results in the October 2001 list. Except the player listed is Tony Miles! There are no more results until January 2007 which are for Andrew F Footner.