An Post Lost My Parcel, and Their CS are Useless. What Are My Options?

You have no contract with An Post (this doesn't mean they have no responsibility to you), take it up with the sender.

As long as Customer support was not on Facebook as a scam page is there , very hard to contact them about lost mail and not answering emails.

I missed a delivery as doorbell was out due to power cut and drove around the area and nabbed him nearby and saved him going back to the sorting office with it.

I would think your packet also went into your local sorting office.

Just call to the local delivery office (many open til 7) and try not insulting the person there. Usually that is what can cause the delay.

Would you assist someone who insults you over the phone?

You can be certain fairly derogatory remarks about you are noted on the internal system (yep - all call takers will leave a small comment on the internal tracking) - hence they will not assist you. Technically it is the seller that you contact.

I'll quote your own post

" On two occasions their CS agent disconnected because I called them out on their personal incompetence"

But it is a good way to guarantee CS won't help you.

Just go to the local delivery office. If the parcel is not there, tell the sender you didn't receive the item.

Acually when talking to people be sound whether or not you need them but yeah be nice.