I had a stack of my leftover shabbos (fancy china) plates on my counter after shabbos, and I made frozen pizza in a toaster oven on motzai shabbos. After the pizza was hot, I took the pizza out of the toaster. The pizza was stuck on a sheet of aluminum foil. As I tried to disconnect the pizza from the foil, the hot pizza hit into at most 2 of the china plates for literally a split second. I also am not sure if the cheese of the pizza or the crust of the pizza hit the plates. Also the area the pizza hit into of the plate was just the side of the plate because the plates were stacked. The area that cheese hit of was at most the size of a dime. The plates were clean on the sides as well. Is this a problem?
You can be lenient concerning the plates, and continue to use them without takiing any action
Sources: The ruling is based first and foremost on Chamudei Daniel, which is cited in Pischei Teshuvah (105:5), who writes that contact for an instant does not create a prohibition. Although many dispute this, Peri Megadim (92:30, 38)implies that there is more room to rely on his opinion where no liquid is involved. In addition, some write that although one may not be lenient concerning prohibited foods, the question of meat and milk is more lenient (Peri Hasadeh 1:36; see Maharsham 2:20). In our case, there is a substantial loss in throwing out the plates; it is probable that the plates were used only as a keli sheini, and furthermore, the bliah would not be more that a kelipah (a very thin layer), and the fact that we we do not know its location provides further room for leniency (provided there is 60 times the volume of the absorbed amount).