Permanent Resident Travel Document - Urgent

[Ssharif7]

Hi guys, I'm a Canadian permanent resident with an expired PR Card and I plan to travel back to Canada on September 7th. I'm currently in the UK as I came to visit my extremely sick mother in an emergency. I mistakenly thought that my PR Card was expiring in Nov 2017 but it expired in Nov 2016 and I only discovered this the night before travelling. Before boarding my flight I was escorted by my airline to immigration due to my situation and I was told that I needed to apply for an ETA. Upon arrival, I tried to apply for the ETA but was surprised to see that this does not apply to permanent residents and that I need a PRTD. However I do not have many documents with me apart from my proof of landing and my expired PR Card. I have been living in Canada continuously since September 2013 so I do fulfill the residency obligations but I'm unsure of how to prove this without any documentation. I know this is a complicated situation and any help would be appreciated.