because... he wasnt completely destroyed if he was... he wouldnt be able to regrow... his last cell was a bone cell that was covered in adamantium... naturally... when his bone Cell grew it grew with the Adamantium... 
 
EDIT:
 
so his bone re-grew as a adamantium bone... so then his adamantium bone grew blood, muscle, etc tissue that grew inside-out(if that makes sense)... of his adamantium bones... 
 
SO NOW U KNO

The Adamantium on his bones remained, protecting the bone beneath which contained living cells enabling him to heal. 

" The Adamantium on his bones remained, protecting the bone beneath which contained living cells enabling him to heal.  "

" @John Valentine said:

" The Adamantium on his bones remained, protecting the bone beneath which contained living cells enabling him to heal.  "

doode... common... that was my explanation... hehehehehhee... but i guess u said it more articulately "

" @Yung ANcient One said:

" @John Valentine said:

" The Adamantium on his bones remained, protecting the bone beneath which contained living cells enabling him to heal.  "

doode... common... that was my explanation... hehehehehhee... but i guess u said it more articulately "

no it wasnt, are you high?  you said that one cell with adamantium coating it remained, meaning that it grew back (including the adamantium?)while john explained that the entire coated skeleton remained a vast difference "

" @hdorman1 said:

" @Yung ANcient One said:

" @John Valentine said:

" The Adamantium on his bones remained, protecting the bone beneath which contained living cells enabling him to heal.  "

doode... common... that was my explanation... hehehehehhee... but i guess u said it more articulately "

no it wasnt, are you high?  you said that one cell with adamantium coating it remained, meaning that it grew back (including the adamantium?)while john explained that the entire coated skeleton remained a vast difference "

Well GOOD MORNIN' To u too...  but he said... what i was tryin to say... "

 @hdorman1: yea... well its a long story... why i said Good Mornin... and its 2 am... here... i had a long day... and, its about time i go... so ah... Bye Hater

No need to argue.  We're all in agreement now :) 
 
It was pushing it, though.  The idea that he could regrow his body from tiny remanet cells on his skeleton, in such a short space of time is a bit much... If his healing factor was that strong, he'd never grow old at all.   
 
I'm pretty sure that X-23 is meant to have a 'better' healing factor because she doesn't has as much poisonous Adamantium in her body to compensate for. 

" No need to argue.  We're all in agreement now :)  It was pushing it, though.  The idea that he could regrow his body from tiny remanet cells on his skeleton, in such a short space of time is a bit much... If his healing factor was that strong, he'd never grow old at all.    I'm pretty sure that X-23 is meant to have a 'better' healing factor because she doesn't has as much poisonous Adamantium in her body to compensate for.  "

He found a spare McGuffin device.  Which, among other things, can restore adamantium bones.

"He found a spare McGuffin device.  Which, among other things, can restore adamantium bones. "

" Did it have a spare copy of his memories in it too? "

Did it have a spare copy of his memories in it too? "

ok you are all wrong. his adamantium was restored by apocolypse. and during civil war he was killed by nitro but had some battle in the afterlife that returned him to life. do none of you ever read wikipedia?

Say what? 
 
I guess there is a logical explanation. Would someone please give it. In normal english, written in english and spelled right. Because it's not if Wiki said it, that it's the truth.

I'm not really sure what the original question is but JohnDaley had it right....kind of..
 
Apocalypse restored Wolverine's adamantium some time ago
 
It was never stated that Wolverine died when Nitro exploded but a few issues later it was explained that back in WWII Wolverine was killed....he was really dead...but he fought the embodiment of Death and won and since then he's been immortal and has had an amped up healing factor....Wolverine made a deal with Death to help him defeat and enemy that Wolverine couldn't on his own and after Death took away Wolverine's amped up healing factor