that sounds like chemical stress on your hair, and yeah, it can definitely happen - especially with such a drastic change from dark brown to blonde. with strong lightening treatments, your hair structure gets put under real strain; the chemicals attack the cuticle layer and can weaken your hair. the fact that you're still losing clumps of hair two weeks later suggests your hair was probably damaged during the coloring or right after, and now it's falling out.
what i'd check: first, whether your hair might already be split or brittle - take a closer look at a few of the hairs that fell out. if they're falling out completely at the root (with that white little knot at the end), that's more like hair loss; if they're breaking off at the top, it's breakage. second, i'd ask your stylist what method and products they used - some salons work too aggressively. and third: what was your hair like before? if it was already dry, chemically treated, or weakened, the coloring could've delivered the knockout blow.
some hair loss shortly after coloring is normal, but losing clumps two weeks later isn't ideal. i'd start with some intensive moisture treatment right now and talk to your stylist - not as a favor, but because you need to understand what went wrong. if the hair loss doesn't ease up over the next two weeks or gets worse, it'd be worth seeing a dermatologist.