If all they were able to see was the first few inches, they did not do a complete colonoscopy and you should be talking to someone about redoing it - at no cost to you. They should have had adequate sedation on hand and qualified personnel around to be able to adequately complete the test. You basically did the whole prep 'for nothing,' and if someone is telling you that that 'result' was sufficient for you to come back in five years, something is very wrong at the facility you went to.
You should be concerned that the facility you used didn't do the job they were supposed to.
I tried to have mine partially sedated and they said I moved too much so they put me out fully. they found an atypical polyp so I am on the 2yr plan but am over due by about 8 mos .. if the next one is clear then I jump to 5 yrs.
I'd insist on a redo free of charge, too.