So, the answer lies in the second book, "Dark Adeptus", and it reads
Justicar Tancred and his Terminator squad could have pooled their psychic power and called up the cleansing fire the Chapter's Chaplains called the Holocaust.They could have forced their way through with their massive terminator armour and Tancred's own sheer strength. But Tancred and his squad were dead, annihilated so completely Alaric hadn't even been able to recover their bodies from Volcanis Ultor. Alaric's squad was on its own here, surrounded and exposed.
So, apparently Tancred's body was utterly destroyed and nothing could be brought back to Titan for the Grey Knights' usual funeral.
But this wh40k wiki tells us otherwise.
Although the Sword of Mandulis was recovered, neither Tancred's body nor his battle-plate were found at the scene of the terrible fight, which has left some to speculate that he might yet still live within the mind-altering eddies of the Warp.
So I'll take the word of god and consider him dead. Another good battle-brother dead, shame.