A somewhat unusual location for a basal cell, since most skin cancers on the back of the hand are of the squamous cell variety.
Although standard of care is certainly to remove any and all skin cancers, basal cell or not, at this stage it could really be followed. Basal cells will declare themselves and form redness, a bump or an ulceration if they recur. The one exception to this, and I have seen this maybe three times, is when a graft or flap is placed over the defect. The basal cell will then "crawl" under the flap or graft and invade surrounding tissue. I had one patient, who felt a fullness near his graft. A biopsy was negative. However, continued suspicious led me to refer him to a dermatologic surgeon who excelled at Moh's surgery. It turned out, he had a basal cell which had invaded down into the orbit of his eye. A day and a half of surgery cleared him, and he kept his eye. No recurrence to date.
A study was done way back in the 1950's when standards were more lax than they are today. A surgeon biopsied basal cells but intentionally left a good portion of them intact. Sis months later, when he went back and examined the patients, 1/3 rd had resolved on their own. The article was published in the Archives of Surgery. A recent review of this landmark article, revealed that the surgeon's study was quite flawed. However, it is very unlikely this study will be repeated. Nonetheless, we dermatologists can recall a number of patients who did not return for years and when they did their basal cell was nowhere to be found. Similar to your case.