There is no certain way within Attaché to be sure that a particular product has had a count recently or was included in a stocktake.
You can look for an Adjustment transaction in Products, Masterfiles, Products, Enquire in Trans (F5) with Type of Adjustment and Reference as "Stocktake", as per screen shot below.
This is the typical adjusting entry that is created when a product has had a count that did not match the In Stock quantity. However, an entry that looks exactly like this could be created manually as well. So, while such an entry indicates a variance, whether this was actually picked up in a full stock take is not certain.
As a result, the only sure way to tell, is from the printed Worksheets created during the stocktake process at Products, Transactions, Stocktake, Print Worksheets. The worksheets will indicate the In Stock quantity at the time, and the count made during the stocktake, if the count sheet was correctly filled in.
If you have not kept these worksheets, then there is no way to be sure.