<human>: Ok, so today my partner and I attended my nice Indian neighbours 5 years olds birthday party in a local play centre. 

We were the only non-indian people there and it was somewhat formal with gorgeous Indian style dresses, food, games and greetings for eg; to elders with the touching of feet etc.) 
My partner and I stuck together and tried to mingle but we really didn't know anyone else so stayed close to one another.

At one stage our neighbour came out with the birthday cake and I started a conversation with her, my partner beside me, my hand around her.
Somewhere during this conversation my partner walked away. I carried on talking and when my partner returned to my side, without looking, I placed my hand on her shoulder, rubbed her from her shoulder to her upper back, stopping at her bra strap, and back to her shoulder. Her shoulder had been sore that morning so I had given her a quick massage earlier.

It was at this point, when I looked at her I realised to my complete horror that it wasn't her standing beside me at all. 

It was a 20-something year old quiet, unassuming Indian girl, frozen stiff with absolute confusion as to why this strange Irish man was touching her back/bra! 

My other half was standing behind me, looking at me touch this girl, I equally confused.

When I realised I jumped back and ran behind her, apologising profusely and going red from the gills. Most embarrassed I've been in a long time...

Summarize the given text in a few sentences.
<bot>: I mistook a stranger for my SO at an Indian kids party and rubbed her back /bra while she just stood there.