Very upset - MOB called from venue - cake was leaning

I want to cry and throw up at the same time, I am so, so, so upset about this. I'm upset that the whole thing happened but I'm also upset that I don't know what happened.

Bride (who is just so sweet) ordered a 5 tier wedding cake. 6-8-10-12-14 rounds.
6-8-10 were white cake (straight box mix, very moist- recipe I have used a thousand times without any problem) with strawberry filling
12 was a snickerdoodle cake (doctored mix) with cinnamon buttercream
14 was marble cake (doctored mix) with chocolate ganache filling

Buttercream icing.

Bride made the cake stand herself. 16 inch round Wilton plate with four 3" pillars (also wilton) glued to another 16 inch round Wilton plate (so the pillars were glued inbetween the plates. Make sense?) The stand was completely sturdy.

The topper was 8 silk roses and a monogram letter (plastic kind you get at Pat Catan's).
I delivered at 3:15. Left at 3:45. I used SPS. Stacked on site. When I left the cake was perfectly fine. I have the pictures to prove this.

Venue calls at 5:45 and tells me the cake is leaning and the MOB wants me to come back and fix it. I was truly stunned to get the call. Reception starts at 6. I race back. I arrive at 6:08 and see that the top 3 tiers are leaning towards the back. The bottom 2 tiers were fine.

I honestly do not know what happened that the top 3 tiers would lean like that. I ended up cutting little pieces of cake board to put under the tiers to kind of prop it up so it didn't look so bad, but of course smooshed the buttercream so had to try and smooth it out to fix it (all this while guests, MOB and groom look on). That part was at the back so I don't think it was as noticable.

I didn't know what else to do. It was warm in the room but when I mentioned that the 2 ladies from the venue got all defensive ("What if it was winter and we had the heat on?"). I don't think anyone moved the cake, but wonder if the table got bumped at all when they plugged in the string of lights underneath the tablecloth. I just don't know.

Sorry this is so very long. I am really at a loss here. I'm also terrified that the bride is going to ask for a refund

If it was the stand, why do you think the bottom two layers were still level and the top 3 were leaning? Wouldn't the whole cake be leaning?

That sucker was heavy!! So now I am wondering if the pillars shifted at all. The stand seemed intact when I went back to try and repair.
I also really wonder if the table somehow didn't get bumped when they plugged in the lights.

Still upset about this and am wondering a)what happened after I left and b)if the bride is going to call.

So no word from the bride yet, but she leaves for her honeymoon tomorrow so maybe when they get back. However...

I think Facebook is going to either be my friend or my enemy here but I am not sure which. Bride and I are friends on FB so pictures of the wedding are showing up (not from her, but her friends are tagging her so I can see the pics).

There are 5 pictures of them posing next to the cake and cutting the cake. In a couple of them the cake looks fine. But in the others it definitely looks like the cake is leaning. I'd love to say it's the angle that the picture was taken from that makes it look like it's leaning, but not really sure if that's the case.

And that makes me wonder if when they get their pictures back fromt he photographer and it's leaning in the professional pictures if she'll start wanting a refund. They spent over $600 on the cake so they expected it to be perfect and it wasn't.

Ugh! I just want to cry and throw up all over again. Sigh....