Neville's mysterious absence

[rach9112000]

No: HPFGUIDX 97948

Hi. In Philosopher's/Sorceror's Stone, Neville breaks his wrist at 
the first quidditch lesson. This is very typical for Neville and is 
an introduction to how Neville's character will be portrayed 
throughout the series (so far), as accident prone and forgetful. 
   However, in chapter 9 (The Midnight Duel), Neville is found 
sleeping in the corridor near the entrance to Gryffindor. He tells 
Harry, Ron and Hermione that he's been out there for hours and 
couldn't remember the password to get in (UK version pg 116). 
Knowing Neville's character, no further thought is really needed for 
this because it's a very believable situation for Neville to get 
himself in. 
  However, firstly I think this is strange because surely someone 
from Gryffindor would have seen him but obviously this depends on 
exactly how many hours Neville was outside for. 
  But my biggest question is, what Neville was doing between the 
quidditch lesson where he broke his wrist and arriving outside 
Gryffindor because he can't have been in the hospital wing with 
Madam Pomfrey for very long, as he tells the trio that:
"Madam Pomfrey mended it in about a minute" - UK version pg 116.
  Neville can't have gone to tea because none of the Gryffindor 
fifth years saw him there as none of them were expecting him back at 
the dormitory that night, otherwise they would have questioned his 
absence when they went to bed (UK version pg 115).
Any ideas?
Rachel