weird thing happened last nite...i decided to open the cap to check my coolant level and it fell apart as i opened it. i was able to get the spring out but the other little rubber/metal washer-grommet thingy fell inside the radiator. anyway i can get this out? will it cause a blockage? can i get it out by flushing the radiator?

i'd rather not buy a brand new radiator if possible any input is appreciated. thx!