Before you carry on...
Hi Jake
Actually read Oort's original paper and the more recent ones since 1950, and then come back. You'll find the reason Oort postulated it is based on the actual evidence from long period comet orbits - data that's hard to refute.
As for IRAS and similar missions trying to see the cometoids - in a word NO. There isn't enough resolution and the signal is too faint.
