So you used the replication method but disabled replication afterwards, is that correct?
If the SEPMs are not still replicating, then they cannot tell each other that a client is connected to one over the other (red arrow icon).
In which case, you're just looking for the lack of a green dot on the client records on the old SEPM.
To be fair, with a default config, the old client records will eventually start dropping off the old SEPM anyway (as they are no longer attempting to talk to it). By default, this will happen after 30 days.