Summarize this article:

It's a pink app with the word "lyft" in bold, white type. It's your image or a silhouette in the upper-left corner of the screen. It's next to a clock icon in the middle menu.   You can only call your driver within 24 hours of the ride. The call is placed through an app that will anonymize your number as well as the driver's. Describe the item you left, when you left it, and make arrangements for the driver to return it to you. Lyft drivers are not compensated for returning lost items, so be sure to tip appropriately.

Summary:
Open the Lyft app. Tap your profile icon. Tap Ride History. Tap the ride during which you lost the item. Scroll down and tap Find Lost Item. Tap Call or Send Message. Talk to or leave a message for the driver.