10 year long resedence ilr missing entry stamp

[jbm]

hello everyone, i am looking from some advice as i am due to apply for 10 year long resedence ilr soon and found one of my entry stamp is missing in passport for back in 2003. it has entry / exit stamps from pakistan but ukba officer in heathrow didnt stamp my passport on arrivel in uk. i did feeled landing card and given it to him.
can anybody advise that is this issue for me? or if not then what sort of docs(old utility bill council letters,doctor letters) or cover letter i should add with my application to explain this.
regards