AIBU to ask that 'wrong' gift is brought back to me?

[hexiestar]

My sister and I have a bit of a tense relationship.
In preparation for my nephew's 4th birthday, I asked sis what I should get him. She said he likes Toy Story, can he have one of the wee toys from that.
Easy enough. Our mum sent me a screenshot of a toy and said 'this one would be good'.
That one was out of stock in the shop but they had a slightly different one, slightly bigger and did more things.
I also got him a few more things as well.
Due to work and travel, me and DP could only come down the day before nephew's birthday but this has been pre-approved by sis who says the day before is actually easier for her, and we'll get more time with nephew and with niece.
When we arrive it turns out sis has taken the kids to an event which is happening an hour's drive away. Not awful, but it means we're getting less time with niece and nephew. And the town that they're going to is a 10 minute drive from the city where we live. So we've driven for an hour, to arrive and find that they've probably passed us on the motorway and didn't think to tell us that their plans had changed. (For added context, we arrived at 11:00am and they didn't make themselves available to us until 15:30.)

Anyway, because it's not the official birthday, sis doesn't want presents opened while we're there. Fair enough. Yesterday evening I get a message thanking me for the presents, she says he loved them. I said I'm glad, hope they were all okay, and if they weren't I still had the receipt.
The reply is
"Aw it's okay dont be sorry - I might be ungrateful and take you up on that though. He loves it! But it's just that the other one matches the sets we got him so he could play with them all together. I'm so sorry to be a d*ck!"
Okay, I'm not away to start an argument over it, so I message her back and say that's no problem, could her hubby drop the wrong gift off to my flat. As he works in the city I live in, and I don't have a planned trip to their town any time soon.
She's not replying now at all now, although she did read the message very early this morning. This usually means she's pissed off.

AIBU to ask for it to be dropped off?
Or was I wrong in the first place for getting the wrong toy?

This whole thing is strange to me. He liked the toy didn't he? It doesn't sound like it matters if it matches his other toys.

I used to play with a toy millenium falcon with all of the figures that fit inside missing except for chewbacca. I rammed Darth Vader and Darth maul in there instead, regardless of the fact they were figurines 20x bigger than mini chewie and not canon members of the crew.
I honestly never questioned it, probably because I was 6.

I'd give her the receipt and leave her to it, but I think it's a shame that she plans to swap out a toy he's already happy with.

Just give her the receipt 🤷🏻‍♀️She can exchange it. Why all the faff of them returning it to you, for you to exchange it, and then sending the gift back? Makes no sense.

I find it silly she's saying he loves it, yet wants to exchange it. Seems sad.

I don't think there's anything wrong with the message. I understand about the size thing - years ago DS wanted some Ninja Turtles, and someone bought a different size to the others he had - I mean like twice the size!! So we swapped it. The bit about them going out though: that is incredibly thoughtless. I would be really pissed off. I wouldn't have stayed. MIL did something like this years ago: DH and his DBro arranged to go to her house on Mothers Day. 'come at 2pm' she says. So they do, and she's not there. Her (2nd) DH lets them in: he doesn't know where she is. Mobile switched off. She came home at nearly 4pm, unapologetic and seemingly surprised that they're not happy. Ironically she did exactly the same thing a couple of months later on her birthday, only this time no-one at home at all. Luckily we live close by, but still very thoughtless.

Your sister sounds like an ignorant, ungrateful shit.

You couldn't get the right toy. She wants the toy to go with the set. Just give her the receipt.

He's 4! Trust me he cares not one jot that his toys don't "match". This is her issue. Post the receipt and leave her to it