How long does it take to pass a letter on?

I got a bee in my bonnet about the National Trust's Titanic events at Springhill and wrote them a letter asking for some clarity on their thoughts. That was mid February. End of February they asked me to confirm my name, as since getting married I'd not updated my name on their system, so it didn't tally with the membership number I'd provided. 

Then, nothing.

I wrote again mid April, asking if they had progressed any further, and querying the wait. They rang to check my postcode, saying that a letter had been sent to me, but the postcode on their system didn't match the one on my letter. Being dumb, yes, that was my error. I've now had a letter, which says:

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"blah blah thanks for feedback, valued blah. You letter has been passed to the DEPARTMENT department, blah they'll deal with it and be in contact"

So, does that mean that after all this time, the letter they sent, which was mislaid, and has now been sent a second time, was merely the letter to say they'd received my letter rather than a letter replying to my letter?* 

More worryingly, what is this DEPARTMENT Department, and will I be invited to join them for a chat in room 101?

In other news, all the events I was asking about have now actually happened, but that's by the by to finding out who thought them up in the first place!

*Whoops...and I've gone cross-eyed