It took a little while, but I finally did get confirmation of Alfred Brendel's encores from his recital on Friday evening (I knew I should have elbowed my way to the head of the line...). They were as follows:
1. J.S. Bach, "Andante" from Concerto nach Italienischem Gusto, "Italian Concerto"
2. Liszt, “Au Lac de Wallenstadt” from Années de pèlerinage, Première Année – Suisse
3. Schubert, Impromptu No. 3 in G-flat major from Four Impromptus, Op. 90 (D. 899)
3. Schubert, Impromptu in A flat Major, from Four Impromptus, Op. 142, No. 2 (D. 935)
Mr. Brendel came off stage following each piece, stood for a beat, wiping his brow with a handkerchief, turned on his heel and strode back out on stage. No muss, no fuss. It was impressive, and made the process seem athletic.
UPDATE: I made a mistake on Mr. Brendel's third encore. It was indeed a Schubert work. See above.