Well i'v been doing this quest for quite some time now and i can make like 300k farming this all day ull get the silk drop and the rolberry worth 2k that u trade in selb... quite easy guy the drone.. but i recommend if ur a thief to wait till ur 66 to take him on cuz lizards will aggress u.
Unfortunately, it's not that you traded too early...there's just a chance (along the lines of 30%, it'd seem) that trading a berry will pop the NM. This also applies to Guardian Crawler, and probably the two higher-tier NMs as well.