Well that is a very good point, however the difference here is that the shuttle is on a set tangent that is readily observable while it exits our atmosphere. What I mean by that is once they have reached the edge of the atmosphere... or thereabouts, I can't say the exact altitude, I'd have to look it up, they begin to plane out to start into an orbital plane or tangent. At that point (depending on what your vantage point is) The shuttle would be going in one constant direction either to or from you and would be relatively easy to track.
Once it is in orbit though, it would be just like any other satellite - once you lost sight of it, the next time it 'came around' so to speak - it would be difficult to keep in a standard telescope as it is traveling at orbital velocity. Even the Moon will move quite rapidly across some telescopes. All depends on the power of the telescope, and whether or not it's manual.
Kind of like being on the 2nd turn of a race track... it's easy enough to watch the cars take off and get up to speed... make it around the first corner... then *zip zip zip zip!!!* they're going by so fast it's much harder to track them until they get some distance again. Same thing with watching something overhead... the more directly overhead it is, the faster it seems to be going and harder to track. As it gains some distance from you it seems to slow down and is easier to track until it disappears.
That's just the way I break it down in my mind anyway.
Take care,
John
On a personal note, as far as the shuttle is concerned: I am a HAM radio operator and have been since the 80's. I was fortunate enough to make contact with the shuttle once and have a QSL card from them!

It was on 2m FM Voice transmission and it was pretty darn cool when I got that card in the mail some weeks later!
So there is another conundrum as far as NASA's involvement in the conspiracy... somehow they have to cover the (correction:) earth and have radio operators in timed sequence on every flight. It has been a tradition for HAM radio operators to talk with the shuttle crew on various frequencies as they fly over. One of the main ones is 2m FM Voice, they also have someone doing code (Morse code / CQ) and some form of voice transmissions on the lower frequencies as well. Not sure if it's 10 or 15 meters.
So, there's 3 simultaneous frequencies to cover, 24 hours a day, in sequence, around whatever set path works according to the flat earth model that several people around the world during every shuttle mission end up with QSL cards, having talked with someone that sounds just like the astronauts on board the shuttle.
I got mine from Owen Garriott, W5LFL - space shuttle Columbia (SK) in Dec, 1983.