ABS light came on

2003 silver celica gts

ok so i wanted to post a thread in braking but im not allowed to post new threads there so screw it gen discussion.

today i replaced my front left cv axle, rotor, hub and wheel bearing, which all in all not bad, except for the rust because im pretty sure the car has been in Hawaii its whole life.

got it all put back together and im about to leave the shop and realize 1 shim isnt between the caliper and brake pad anymore.. is that enough to make the ABS light turn on in the dash? i was really careful and tied the caliper to the spring when i had everything taken apart. and i drove it home with no problems with the brakes. i didnt notice any leaks.

i would have put the shim back on the brake pad but the shop was closing up and i dont have all the tools i need to lift it and fix it at home. and i only live like 3 miles from home so i didnt really risk anything with the brakes at 25 mph.

thanks for any ideas how i might have messed up the car. but maybe ill get lucky and the light will go off on its own or after i replace the shim.