CIM
The airfield I fly into is fairly busy and it is quite common not to get clearance until as late as crossing the undershoot. The lowest go round I've done has been from about 2ft of the runway.
Last week while doing some circuits I was told to continue as a low approach whilst another aircraft cleared the runway and was given landing clearance while about 50m down the runway at about 1ft from the hard top.
I guess that in a busy circuit the ATC's can lose sight of whats happening, to me that's just one of those things. Usually compounded by someone in the circuit doing something that they should'nt be. Like the prat last Sunday who decided to make an early turn after doing a go round without clearance from the tower. Got a right bollocking over the air.
My neighbour a couple of years back was ATC at this airfield and he ended up taking 6 months off after a fairly hectic time to get his head straight again. I would not do ATC for love nor money and have the greatest respect for folks who do a very tough job. My own inclination would be to forget it and get on with life. It's nothing major.