Examine the Animal Fact Sheet carefully.

The drawings on the note are food items animals at the zoo eat.

Every food item in the drawing is mentioned on the Animal Fact Sheet. Find which animal each food item corresponds to, then translate that into a letter (each food item represents a represents a different letter).

Pay attention to the first letter in each animal's name.

Each food item can be matched to an animal listed on the Animal Fact Sheet (see the "Diet" section for each animal). From there, translate the food item into a letter by taking the first letter of the animal's name (that eats that food item). For example, the watermelon corresponds to an Elephant which corresponds to the letter E.

Decrypted, the note reads:

Thanks for yesterday. That was really sweet. And thanks for switching with me today. I hate seeing his face.