When Phillipa Soo reminded the cast of the traumatic moment, much of the cast remembered it with her. Okieriete Onaodowan, who plays Hercules Mulligan / James Madison in Hamilton, said he actually thought something was going on stage when she forgot her lines. In an effort to make the actress feel better, Lin-Manuel Miranda deflected to a moment from one of the later King George actors Andrew Rannells, who decided to mouth the “words” to his song when he forgot them in an effort to make the audience believe the sound was the problem.
Article source: https://www.cinemablend.com/news/2550349/hamiltons-cast-reveals-the-worst-on-stage-flub-prior-to-disney-movie