Besides file checking, run this one:
sysutils/testdisk
Chances are, when ran a couple of times, that you will implement proper backup|sync procedures
As most of us do, usually we run fsck -y
in the hope evrything gets fixed.
Remember that a hard disk is a table with entries and pointers.
"Formatting" only set those entries as "re-writable".
Proper test is destructive, as most manufacturer's hard drive utilities, but these will actually "zero" your drive, mark bad sectors (in yet another table), eventually give you a report to use for a RMA.
Watch fine prints in the warranty (or browse the manufacturer's site): some drives carry five years (wheter manufacturer's, or national distributor, or local outlet).
I keep a table of serial numbers and dates and test in due time.