The parcel has not arrived

and I am feeling angry, upset and disappointed.
Ten days ago I posted a small birthday present to our beloved R... my sister-in-law.  R... is one of the world's good, loving, warm, caring people.  My brother frequently refers to her as "the best person who ever happened to him".
She doesn't want a fuss made of her birthday but we like to acknowledge it with something small. The Senior Cat entrusts me with the buying or making of something and sending it to her.
This time I bought a really lovely hand painted scarf in colours I know she loves. It was light but warm and I knew she would appreciate the workmanship in it.
I took it to the local post office and the person behind the counter said, "That can go as letter size I think".
She found the appropriate envelope, weighed it. Yes, letter size. I handed over the address label I had typed. I watched her tape it very securely to the heavy duty envelope. 
      "Priority?" she asked
We agreed it would be a good idea. I paid for the postage and watched the stamps go on. The postal worker tossed it gently into a box behind the counter ready to send.
I went off confident the little parcel would arrive.
My confidence has been misplaced.
Yes, perhaps it got tangled up with something else but it should have been untangled and sent on. 
It is much more likely that it was delivered to the wrong address (even though I had the correct one on the envelope) and someone has not been honest enough to put it back in the post or a postal worker hasn't been honest.
I don't doubt the honesty of the local person. I know her. I have known her for a long time.
I suppose I should have sent it registered and insured but... I paid for it to be delivered.