TLC does not show spots in many O chem labs

Why TLC does not show spots in many O chem labs ?

In Beyond Labz, the solvent system is 20% ethyl acetate in hexanes. Reactant and product molecules that are highly volatile (low boiling point and high vapor pressure) or very nonpolar (with no affinity for the silica molecules coating the TLC plate) will not be seen on a TLC plate. These molecules either evaporate too quickly or are pulled off the plate and into the solvent system when spotted. Also, to aid the user in focusing directly on the reactants and products of a reaction, reaction solvents, reagents added from the bench, and reagent byproducts will not be shown on TLC plates. All spots belong to either a reactant or a product molecule. This is why you are not seeing spots every single time.

Kelsey