AZOI.IS -“Get a white ink permanent marker and write your name and tel number on the inside somewhere. Someone might call you to return it.”
This is only good if you only bring it to Jewish places, like when you hang up your coat. How many people have never had a coat switched or lost? I’ve had my Lulav and bag taken and the one I have in return isn’t even the same. Close, but pretty obvious it’s different.
I wouldn’t put my name and tel # on my umbrella. What if you lose it in Shoprite? Do you really want some low-life having this info?
Esp. in our day and age where indentity theft is rampid.