Who they voted for is immaterial.
The point is that a voter who participates in one party’s primary is not, by law, allowed to vote in another party’s runoff.
That makes the Tuesday ballot of any such voter invalid, regardless of how it was marked. The vote doesn’t move from one candidate’s total to the other’s, but is thrown out.
Sorry, but ballots are not identified as to who cast them.
I don't know about you, but when i vote, my name is not printed on the ballot anywhere.
It's one of the reasons electronic elections (internet based) are hard to do and audit properly. It's not like an ATM, where you identify the person, and the account and can keep the books auditing the transactions. Once the vote is cast, it is anonymous. Guaranteeing anonymity while at the same time, validating that the individual is a legitimate voter is harder to do electronically than you think. Done right, it involves cryptographic blinding protocols.