Batman was waiting for the Flash to arrive after the latter promised to be in the batcave in one minute.
The letter that Reverse-Flash tore up was the one given by Thomas Wayne in the Flashpoint Paradox universe to his son Bruce Wayne in the New 52.
Batman lost this fight as shown in the other pages.
From – Batman Vol. 3 #21
That Comedian’s pin in the first panel…. JDR played Comedian in Watchmen.He also voiced Thomas Wayne in Flashpoint animated. Thomas Wayne being Comedian could explain why his letter could travel across time/ between universes (transcending time traveller’s paradox)… and also that he is keeping a watch on his son. Lmao. Nice idea for a fanfic, anyways:P
JDM (not R) played Comedian, AND Thomas Wayne in Batman V Superman in additional the Flashpoint animated.