I've googled around and is there a difference between these two spellings? Are both accepted. My initial instinct was that the first spelling is incorrect, but appears to have some usage.
As mentioned, both spellings are generally accepted and found in various sources. The spelling "uncatalogued" seems to be more popular in general, based on the Google Ngram Viewer result shown in the figure below.
I think this is based on the variation in the spelling of the word "catalog(ue)".
I would imagine that anyone who uses the spelling "catalogue" exclusively would also use the spellings "catalogued" and "uncatalogued".
But people who spell the verb "catalog" would be expected to use the spellings "cataloged" and "uncataloged', I think—although this seems less certain, because some verbs do add a letter in inflected forms, like "program/programmed" or "picnic/picnicked".
It may be useful to split the Google Ngram Viewer data by country:
You can see that in British English, where "catalogue" is the preferred spelling, "cataloged" is extremely rare, while in American English, where "catalog" is more common than "catalogue", "catalogued" and "cataloged" have similar frequencies.
"Uncatalogued" and "uncataloged" are much less frequent than "catalogued" and "cataloged", but seem to show similar relative frequencies: