I hate to be the "bringer of bad tidings", but mirage is what the long range shooters use to determine wind deflection. The mirage is used to determine how much windage to add to the bullet. Not seeing heat mirage is a bad thing if good quality glass is what you are after. Good quality glass shows every bit of mirage. That is why your higher quality spotting scopes have a lower power selection, the lower the power the less mirage you will see in high quality glass. Usually the trade off is between 16X to 20X.

So by not seeing mirage on a hot sunny day is actually a bad thing-especially at higher powers of magnification. If the glass was of good quality then everything would show up(including all mirage). Which you say it wasn't?? Tom.