Since you've lost your sim you can retrieve your number, as long as you have access to your account. You could perform a sim swap, this transfers all your old details (Including your number), airtime credit and remaining goodybag allowances to a new sim.
Do you mean that you don't have the IMEI number of the phone because you don't have the packaging for it anymore?
It shouldn't be a problem because if you haven't used your SIM since your phone was lost (I take it your phone was lost with the SIM in it) then the system will still have your phone logged as the last phone used (and the IMEI will still be stored).
You can select to bar your phone and SIM and a new SIM will be sent to you automatically. You can read about that here