Post [Q] android 4.4.2 (system update files ready to install ) gets DELETED automatically

hi everyone
recently i am facing few problem with my Nexus 7 2012 , android 4.3 , non rooted

1st - I am facing copy bug which is crashing any app from which i copy and
2nd - which is quite strange
my 4.4.2 update (which has been downloaded for quite sometime and was ready to install) gets automatically deleted
and now its showing android 4.3 as upto date whwnwver i check for update in settings..
where are my 4.4.2 downloaded files i have no idea...
i havent deleted anything

Any help!!
Is this some sought of a bug or system update file which has been deleted will get replaced by android 4.4.4 later ?
have i done something wrong
i am all confused ..
plz help