I encountered the following sentences in a picture book:
"Something is crying, Minneapolis Simpkin," I said to myself. "I will find out what it is." I looked in the bushes. Was I surprised! "Wow! A baby monster!"
I think "Was I surprised!" is a exclamatory sentence. What kind of sentence pattern is it?
Beautiful and accurate graphs by snailboat.
Yup, that's definitely exclamatory. I believe it's a shortening of a structure used in storytelling. One might say "Was I surprised? You bet I was!" Kind of an old format. No recently-made book has actually used this or your example's format.
Generally, the question mark and exclamation point are very accurate markers for figuring out the intended meaning. "What?" and "What!" are two very different phrases for this reason (the first asking someone to repeat themselves or to ask why they are doing something, the second to display surprise or disbelief).
