I have just found that you can "track" your PR Card delivery, and it´s pretty silly.
Check your "Document Status" section at your PR Card application, in your MyCIC account.
If it says something like "We have mailed your PR Card. It may take about six weeks to be delivered...", this means IRCC has no confirmation whether the PR Card was received NOR returned.
If it changes to "Your document is valid", it means the PR Card has been either delivered OR returned. You can only be sure of which by calling IRCC 1-888-242-2100, options 2, 3, 0 (LOTS of patience to be able to speak to an agent, THEN to wait for the agent), and then verify this possibility.
If the card was returned by Canada Post to IRCC, they´ll tell you. The agent will then verify the address, update it if applicable, and re-issue the PR Card, this time urgently and with a timeframe of 15 days. You can verify the same for your spouse and dependant children, just make sure you have UCI, complete name and date of birth for everyone (including you).
That has just happened to me. Our PR Cards were returned and received by IRCC May 28. I found odd that the message had changed at MyCIC portal so I googled about it, and found out about being able to track a possible PR Card return. I already figured out what happened with my friend in Toronto who gladly handed their address as our mailing address for basically everything (we´ve soft landed, so we´re kinda on the clock now to avoid a PRTD request), and I should receive our PR Cards this time.
This changes my timeline to:
Landed: May 2 (Pearson International)
Linked applications: May 3
Ghost update, approved and mailed: May 9
Returned to IRCC: May 28
Re-issued to same address: May 31
Good luck everyone!