Can anyone see my phone number?

No.  Not unless you enter it in the main part of the message when you’re contacting an Owner (or Finder).

If you’re a member of WhosMyOwner.com your mobile number is in your account if you’ve added it, but we don’t send it to anyone – we just use it to forward Finder messages to you.  Text messages from us are sent from our own number, or from “WhosMyOwner”.

If you’re a Finder, the Owner you’re contacting can ONLY see the message body you enter, so if you want them to be able to contact you to arrange collection you must provide details in the message itself.