Here the original manuscript reads catched (spelled as cacht) instead of the standard past-tense form caught. Oliver Cowdery, when he copied from 𝓞 into 𝓟, replaced catched with the standard caught. Oliver was also the scribe in 𝓞, which makes one think that catched must have been what Joseph Smith dictated. Moreover, Oliver initially wrote cacht as caghed in 𝓞, which he then changed to cached with erasure and overwriting (and ultimately, with further erasure and overwriting, to cacht); the initially written g in caghed seems to show that Oliver was thinking of writing caught but that he consciously decided otherwise. It is natural to suspect here that the nonstandard catched represents Joseph’s dialect, especially since elsewhere the text has only caught for the simple past tense and the past participle of the verb catch (eight times).
Even so, there is considerable evidence that in Early Modern English catched was an acceptable past-tense form for the verb catch; according to the Oxford English Dictionary, the form catched was common in literary English from Middle English up into the 1800s (the alternative caught was also common during this time period). Only in the 19th century did catched become nonstandard and restricted to dialectal usage. The online OED provides numerous examples of catched from writers of literary English, including these examples (with original spellings retained):
The first example comes from Coverdale’s biblical translation of Judges 15:4. Thus the use of catched is possible in the original text of the Book of Mormon, and the critical text will therefore accept it (although the possibility remains that catched may be the result of Joseph Smith’s own dialect). For another example where the original text has the standard past-tense form except for one instance, consider the case of drowned versus drownded, discussed under 1 Nephi 4:2.
Summary: Accept the use of catched in Alma 36:18, now nonstandard (“now as my mind catched hold upon this thought”); Oliver Cowdery ended up spelling catched as cacht in 𝓞; the form catched was a common past-tense form in earlier English.