I looks like you may be mixing up OpenFL APIs and Starling APIs. Starling’s TouchEvent class has a getTouch() method that works that way. However, OpenFL’s TouchEvent class does not. While many parts of OpenFL and Starling have identical or very similar APIs, this is one place where the difference is a bit more pronounced.
This chapter from the OpenFL Developer’s Guide might help:
And the TouchEvent class in the OpenFL API Reference: