So, if The Flash is able to see through one of Loki’s disguises, he can instead make himself unable to be seen at all, making “Speedy” unable to tell when Loki will strike a force field around him and trap him before he could even run away.
Norse mythology’s “God of Mischief” and the adoptive brother of Thor has a tendency for trickery that has been of great use to him against his many foes, from altering his own appearance to projecting illusions that effortlessly catch people off guard, but even more useful in that assembly are his abilities in hypnosis, invisibility, and even the creation of force fields with which he can surround himself or anything else of his choosing.