It's the same in both 1904 and 1894..
Pott's lane, Williamstown is included the county Dublin index but there's no mention of it in the street listing for Williamstown or Blackrock.
A number of the smaller side streets and cottages are not included in Thom's, especially outside the city, so I presume that's the case here.
In the areas in county Dublin the side-street junctions do not seem to be included as often as in City section. This detail can be useful as provide approx locations for smaller unlisted streets in the city area.
e.g. the listing for Grafton has numerous side street detailed, whereas no side streets are included in the section for Willliamstown. A single side street is listed in Booterstown.
Pott's lane is mentioned in county Dublin index in Thom's back to 1868 at least .
Shane
p.s. I just spotted it in the index in Thom's 1938... so maybe it still existed then ?
p.p.s. It's also listed in the 1949 & '58 editions as Pott's Lane, Blackrock