iTunes forgetting more and more music files

I have a rather large iTunes collection at around 25,000 songs that I have curated over the years.

I collected this music from Cd's I bought, dvd's I digitized etc and recording of continuation education conferences... yet iTunes seems to randomly forget a few files.

Why can't a computer remember where I put my music (they are ALWAYS put into iTunes...)

iTunes defaults are on, it organizes them.

I never move them

It is an internal HDD

They are random audio files that I just played (6 months ago, 2 weeks ago, 13 days ago) etc

What is going on with my MacBook Pro 2011?

16GB of 1333 mhz ram and 1tb 5400 rpm hdd?

I can't use hardware that is faulty and need NEED to have long term storage reliability (which is why i chose mac)

***!?!?!?!?

Rant is complete, for now

Should I re-ping my iTunes somehow or is this a known "Apple alzheimer's" issue?