Yes, your enzymes can drop that fast, for multiple reasons. You can have GI infections that may transport up into your liver via the common bile duct, and this can resolve itself in several weeks. Also, a small gallstone can cause a mild impedance to your bile, leading to some back flow into the liver. The stone can continue on out into your small intestine, but the backed up bile is a poison to your liver cells, resulting in a temporary enzyme spike. Viral hepatitis-B can resolve its acute phase in short order as well. There are other possibilities of course.
Your doctor should be able to diagnose the cause for you. Was there a particular symptom that caused you to have your doctor check your enzymes in the first place.
A second opinion is a good choice. Quick drops are not typical bit so happen. I see it all the time with my liver disease, but I don't mean to imply you have what I have. Good luck and let us know what you find out.