Since terminal can't find it anyways, I would assume it's safe to move, but I'm not sure how that would affect other files that either rely on ffmpeg install path if they do. FWIW I used
./configure --prefix=/usr/local/bin --enable-cuda --enable-cuvid --enable-nvenc --enable-nonfree --enable-libnpp --extra-cflags=-I/usr/local/cuda/include --extra-ldflags=-L/usr/local/cuda/lib64
to configure the package, then sudo make install in a separate terminal on accident, although I don't think that should make a difference. I had also removed an older ffmpeg after sudo make install but that was a repo package installed in /usr.