eyes wide and mouth open

[diamondcutter]

I cut the map into pieces and handed them over to her, asking her to put those pieces together and make a complete map again.
But within several minutes, she was standing in front of me with a perfect map in her little hands. Surprised, I asked her how she did it so quickly and easily.
She smiled and said." Oh, Dad, there is a man's face on the other side of the map. I just tried to make his face completely."
Then she turned and ran outside to play, leaving me eyes wide and mouth open.

Source: English test paper, Henan Province Senior High School Entrance Examinations, 2020

I’d like to know if “eyes wide and mouth open” is a set phrase.

I wonder whether “leaving me eyes wide and mouth open” can be paraphrased like this.

“leaving me with my eyes wide and mouth open”

 

[probus]

I don't think it's a set phrase because I don't recall ever seeing or hearing it in exactly those words. Your rephrasing is fine and probably more likely than the original.

 

[Tdol]

It's not a set phrase. Wide-eyed with my mouth agape might work.

 

[Tarheel]

I cut the map into pieces and handed them over to her, asking her to put those pieces together and make a complete map again.
Within several minutes, she was standing in front of me with a perfect map in her little hands. Surprised, I asked her how she did it so quickly and easily.
She smiled and said." Oh, Dad, there is a man's face on the other side of the map. I just tried to make his face complete."
Then she turned and ran outside to play, leaving me with my eyes wide and my mouth open.

Source: English test paper, Henan Province Senior High School Entrance Examinations, 2020

I’d like to know if “eyes wide and mouth open” is a set phrase.

I wonder whether “leaving me eyes wide and mouth open” can be paraphrased like this.

“leaving me with my eyes wide and mouth open”

Yes that's a big improvement over the original.

 

[diamondcutter]

What about rewording the original "leaving my eyes wide and mouth open" like this?

"leaving my eyes wide and mouth open"
Or:
"leaving me eye-wided and mouth-opened"

 

[tedmc]

It is a set phrase but in Chinese. It looks like a direct translation from the Chinese idiom which has no equivalent in English.

In English, the closest words I can think of are startled (with a startled look), dumbfounded, open-mouthed.

 

[Phaedrus]

Or:
"leaving me eye-wided and mouth-opened"

You definitely shouldn't say that. I think you're trying to say "leaving me wide-eyed and open-mouthed," which does work well.