Matching non-escapped quote with Lua pattern

[Andrew Starks <andrew.starks@...>]

I'm having trouble finding a pattern that works for finding an
unescaped quote in a string. So:

[[\']] should not match

[[']] should match

I can get it to work with  '([^%\\]")' , except at the beginning of the string.

Here is a complete example of my issue. Note that the problem is in
the first result. Results 2 and 3 are fine:

``lua
pattern = '([^%\\]")'

s = "\"'[==[ sdhfjks ]===]\\\"'"
print(s:find(pattern))
--> nil

s2 = "\"'[==[ sdhfjks ]===]\"'"
print(s2:find(pattern))
--> 20 21 ]"

s3 =  " \"'[==[ sdhfjks ]===]\\\"'"
print( s3:find(pattern))
--> 1 2 "
``

My pattern matching skills are out of solutions, except to check the
pattern twice, once for in the beginning and then again for elsewhere
in the string. Is there a way to do this with one pattern?

-Andrew