Although this doesn't give you tracking when someone types in the number, if they click on it from their mobile phone you'll be able to register a click and can even log that back to Salesforce with a query, automation, and journey.
When deleting subscribers out of SFMC, mobile studio deletes all subscribers with that common phone number, not just those that have that subscriber key. You have a limited time where the deletion can be stopped without help from SF Support and SF Support can take days to stop a deletion. Always set a minimum suppression period of at least 7 days.