I would say (with Aquinas, if I recall correctly, it was more than 30 years ago …) that the "substance" of IHS's body is the resurrected body - now, so that in which we share is the resurrected body. But those in the upper room shared in the living, not yet died, not yet resurrected body. I haven't really seen much argument on this, but for me it is not impossible for Jesus to have reached forward (so to speak) to access sacramentally His Resurrected Body before the events had unfolded in human history.
Just a thought.
Aquinas suggests that the substance is the substance of the body of Christ, "at the time" so to speak. So, Holy Thursday, living, not yet died, Christ's body. From evening Good friday to maybe 0000 hours (or who knows when) EaSter day, substance = dead Christ's body. Ever since, Risen Christ's body.
I don't have those volumes of the Summa.