(a) Ein meshalmin al pi atsmon Rashi explains that they were Muzam in Beis din & the Baal din didn't have time to bring them to haamodo bedin & they were Moide at another Beis din .
Isn't the mitsva of Veasisem loi ka'asher zomam a chiyuv on beis din IRRESPECTIVELY if the baal din sues or not ?
(b) Daf 4a : Vecheen kikor shel terumo shenofal shom tomee. mai vecheen mahou deteeme hosam oike gavre achazokee , hocho oike terumo achazoke ko mashma lon .
Why al pi ho emes dont we go bosar the chezkas taharo by the kikar shel terumo ?
(a) With regard to Malkus and Misah, we certainly judge him even without any claim from a plaintiff. However, with regard to the Chiyuv Mamon of the Edim Zomemim, it is not possible to judge them without the claim of the person to whom the Edim will have to pay, since it is in his power to forgive them and exempt them from paying, if he so desires. Accordingly, bringing Edim to court is meaningless if the Ba'al Din does not want to collect money from them.
(b) In truth, there is an even stronger question. Why do we not say that the Kikar is Tahor (at least if there were more than three people present when it fell there), because it is a case of Safek Tum'ah in Reshus ha'Rabim, which is Tahor? (However, it could be that we apply the principle of "Safek Tum'ah b'Reshus ha'Rabim Tahor" only in a case in which the object about which we are in doubt has a Chezkas Taharah; see Daf Insights to Sotah 28:2. Accordingly, this indeed might be the intention of the Gemara here, which initially suggests that the Kikar should be Tahor specifically because of the Chazakah. According to the Rishonim who maintain that even without a Chezkas Taharah, we rule that "Safek Tum'ah b'Reshus ha'Rabim Tahor," the question certainly remains.)
It must be that in this case, even though we cannot say that it is a certainty (Vadai) that the wine remained in one place, nevertheless it is a "Safek ha'Matzuy " that it remained in one place and can thus be Metamei the Kikar. (This is as the Rambam writes to explain the words, "Iy Efshar l'Sheloshah Lugin...," which Rashi deletes in DH Iy Efshar. Rashi will agree that it is a Safek ha'Matzuy, and his intention is merely to prove that it is not a Vadai.). A Safek ha'Matzuy has the status of a Rov with regard to Tum'ah, and in a situation of a Rov we do not apply "Safek Tum'ah b'Reshus ha'Rabim Tahor," as the Gemara teaches in Kesuvos 15a.
It is for this reason that we do not follow the Chezkas Taharah of the Kikar.