Was it between his meeting with Sarek and his meeting with Admiral Morrow? Keep in mind that beforehand, Sarek himself said that Spock's body was in death. Meanwhile, on the Genesis Planet, David Marcus and Saavik discover that Spock's body is not only both alive, but cycling through the various stages of aging. This however, is not related back to Starfleet.
share(Answering mostly for posterity and not because I necessarily expect the OP is still wondering years after the fact.)
Kirk and crew have no idea that Spock's body has been revived until the moment they hear it from Saavik when they've made it to the Genesis planet. They haven't gone there because they think they can resurrect Spock, they've come to retrieve his body to be memorialized on Vulcan. They're also hoping that by participating in this ritual it'll clear Dr. McCoy of his odd mental condition stemming from his impromptu mindmeld with Spock.
They never say this in so many words, but the katra ritual is more or less a funeral service. What Sarek is really asking of Kirk is a chance to bury his son and preserve his memories (it's explained in the script and novelization that the katra's are traditionally collected in a hall or temple on Mt. Seleya). The priestess even reminds Sarek when he asks for the "fal-tor-pan" refusion ritual that it's just a legend (ie. a tradition, a myth, it's not supposed to be literally real), probably tantamount to asking a modern-day minister to perform an exorcism or some such.