Item not received - or so the customer claims

Hi, guys!

As the title suggests, I need a bit of guidance please on a current situation I’m facing which I had yet to encounter thus far on Amazon or beyond.
Personally new to selling on Amazon, but not new to the online selling world and the vast and wonderous adventures it brings along with! - haha

The situation is the following:

I sold a seller fulfilled item last weekend with an estimated arrival time of 3rd to 4th of November.

I get a message earlier this morning from the customer upset that his item had yet to arrive and in the meantime he had made alternative arrangements so would like a refund on his purchase.

Checking the tracking on the DHL website I noted that the item was delivered on the 3rd of November in the morning, signed for (by the driver of course as it is customary nowadays) and thereafter left behind the wheelie bins - picture provided.

I informed the customer as such and provided pictures I had from their website.

His reply was that he did not appreciate me implying that he is a liar as a retired ex-vicar - if he says he doesn’t have it, well, he doesn’t have it basically - and as far as he was concerned the courier driver should have never left the parcel there as he lives on a very busy road and someone must have taken his parcel as he never found it and left no card behind either informing him the item was left in that particular spot.

Mind you, while I think we can all agree some customers do try their luck at times, I don’t view all claims as potentially fraudulent and “out to get me” and I was nothing but open, friendly and professional with him, so not too sure why he thought I was implying he is lying. I genuinely wasn’t. I was simply providing him with the info I had on my end from the courier and kindly requested he checks with his neighbours and family members in case someone took the parcel in for him without his knowledge.

Anyways, that is the situation I’m currently having and not entirely too sure how to efficiently deal with it. I’ll get in contact with DHL tomorrow and see whether they can help out in any way.

In the meantime, does anyone have any wisdom to share?

Or where does this whole thing stand?

As it is marked as delivered do DHL wash their hands off? Even though they left in somewhere on the premises where it MAY have been stolen from?

Do Amazon side with the customer regardless of the delivery being recorded? - case is not opened yet, but I assume if this does not go the way the customer wants he will eventually open a claims case with Amazon.

If both DHL and Amazon wash their hands off somehow, then I must support the cost of refund myself I assume.

Or am I right in assuming that as long as neither myself neither the customer designated a safe place for drop off, the courier SHOULD have dropped the parcel with the customer directly? Thus making them liable for INR claims?

Any input welcome! Thank you (and sorry!) for reading (so much! haha)