Grammar

I would have written..
I took the wrong bus. Happily, when I reached the supermarket I bumped into a friend who had taken the wrong bus as well.
or
I took the wrong bus. Luckily, I bumped into a friend at the supermarket who had taken a wrong bus too.
or
I took the wrong bus. Fortuitously, when I reached the supermarket, I bumped into a friend who had done the same thing as me.

…a friend having taken the….

Hi dalehileman,
is this unacceptable?
'a friend taking a wrong bus as well. '

I'm no grammarian. I think it's okay but maybe not colloquial

Thank you

Not at all Jane. However don't rely on my observation since the meaning "colloquial" varies depending on who's using it

I took the [1] wrong bus. Fortuitously, I reached a supermarket and bumped into a friend taking [2] the [1] wrong bus as well.

[1] The bus you and a friend [one of many friends, not the only friend] took was not one of many buses, Jane. It was a specific bus to each of you in your own personal situation, the wrong bus, hence the 'the', which denotes specific.

'fortuitously' is out of place in such casual speech. There are many other choices much more suited to the register you are using.

As luck would have it/Coincidentally, I stopped at a ... .

[2]
taking - As you would both have had to have gotten off the bus to meet and discuss the situation, 'taking' is not appropriate.


and bumped into a friend who had taken the wrong bus

JTT as an oldster I'm a bit confused here but wouldn't he say "..also taken…."?

But using "the" suggests, if only ever-so-slightly--that they might have taken the same bus at the same time