Have you ever seen a piece of art, and found yourself at a loss for words as to how to comment on it? (Google)
After all, with a full repertoire of cliches at their fingertips, rhetoricians will never be at a loss for words. (Google)
Lazy, busy, or just at a loss for words? Oh, I don't even know. I want to say more but life is so overwhelming lately. I hardly know where to start! (Google)