Pop up on screen during exam

Sat for REG this past Friday. During the exam right after my break there was a pop up that came up on my screen and instantly vanished. It happened so fast I couldn’t read what it said. The testing center employees said that happens sometimes and that my attendance report looked normal. Has this happened to anyone before? Should I be concerned about the completeness of my answers and see if all my testlets were received? NASBA status is attended.