How can I add a phone number in a URL query string in CiviCRM?
Goal: To bring up all records associated with that number
It depends what you mean by "all records", but the custom search called full-text search (under Search - Custom Searches) can be made to run via url like so:
That will bring up the contact with phone 894-1515.
If you want to include activities and such, then leave out the "table=Contact" part.