Dear Paul,
No. I've never heard of the Liturgy of St John Chrysostom being celebrated on Holy Thursday rather than that of St Basil. Of the five Vesperal Liturgies appointed to be celebrated during the Liturgical Year, only that of the Annunciation has St John Chrysostom's Liturgy rather than St Basil's.
I assume that you knew it was St John Chrysostom's Liturgy because the priest said the mystical prayers aloud? That's not traditional Orthodox usage, though Greek Catholics may be doing that now, as are even some Orthodox.
Happy Easter!
Fr David Straut