The problem actually is that if for example a slave is suddenly disconnected from master while a read or write cycle from/to it has not been completed, the master goes into an unkowm state which stops it from further read or write from/to other slaves.
are you saying that these devices are "pulled" with power on? What kind of system is that?

As you said the master is still waiting for ACK or the next bit of a incomplete byte of data, when the addressed slave is disconnected. But I dont know how to stop master from useless waiting.
with a "master" with IIC hardware it should be fairly easy, there is the status register which you can monitor that will tell you exactly what is going on.

Erik