There are 2 telltale signs of thrips:

one is if the leaves of the flowers are dusty with pollen, i.e. the
thrips munch on the pollen and leave it all over the leaf and 2,
if you hold the plant on its side and tap it gently over a piece of
white paper, thrips fall onto the paper and look like grains of sand.

One of the ways that people like me buy and bring home large volumes
of plants from strangers (shows) and faraway places and try to avoid
bringing home bugs like thrips, is we *always* disbud any new plant
before bringing it into the house, i.e. take all of the flowers and
flower buds off of the plant.

I hope this helps,
Cynthia