I have claimed back over 15K now from various organisations including overdraft protection (that was a rather splendid 8.5k) I did it myself, do not use a claims company!!
Yes, it should show up on statements and you may not have had it, then again you may have on old cards and overdrafts you no longer have the paperwork for.
Some people had it added without their knowledge, some had it sold to them even though they would not have been eligible to claim (self employed and so on) others (me) were told they would not get a laon without it.
I have also claimed for a mis-sold packaged bank account (monthly fee) I was told this was the only way I would get an overdraft, crap! this was my last claim and I got back £900 2 weeks ago.
Most banks now have a link on their websites to put in a claim, most of my questions I answered "cant remember" (with dates mainly)
remember, you may never have had it, if you did it was not necessarily a bad product for you, it is not in itself a terrible thing, it was the mis-selling.
Have a read through the PPI boards on MSE, a wealth of advise!