Retrieving a contact that I called and talked to on Telegram, but accidentally deleted I talked to this person on Telegram (sent many messages, exchanged pictures), and then called them a few months ago via default Calls Android application. 

Contact was deleted (call logs too), and Telegram chat / contact deleted as well. 

Is there any way I could retrieve this person's telegram contact, or telephone number? 

Telephone company only saves 1 month call logs (Vodafone).
The following steps from How can I recover deleted Telegram chats? should work:


  Use the iKeyMonitor app to recover all the messages that you need quickly.
  
  
  Sign up
  
  
  Sign up for a 3-day free account of iKeyMonitor to recover deleted
  Telegram messages.
  
  
  Log in to the Cloud Panel
  
  
  Log in to the Cloud Panel to download iKeyMonitor to the target
  Android phone or iPhone.
  
  
  Install iKeyMonitor
  
  
  Install iKeyMonitor and activate it with your license key.
  
  
  Start Recovering
  
  
  Start recovering deleted Telegram messages on Cloud Panel.