There is a debate in the study of biblical Hebrew as to whether the Qal stem is only ever used in an active voice, or if such a thing as a Qal passive (Qp) exists. The Masoretes said ‘only active’ but many disagree. A simple Bibleworks search yields 85 accounts of a Qp.
A simple answer is this: that a passive nuance for the Qal stem does exist, but Qp forms themselves do not. When Qps are used they ‘borrow’ forms from other stems (usually Pual or Hophal). For example Ruth 4:17 has יֻלַּד.
Why, then, are such froms not recognised as simple Pual and Hophal forms? It is because their conterpart stems (i.e. Piel and Hiphil) are often unattested. It is unusual for a Hebrew root to exist only in a passive stem. Therefore, it is concluded by most scholars that such forms are Qp.
Weingreen (p150-151) notes that, as with many issues in Hebrew, this question is particularly pertinent to certain roots. Weingreen notes two in particular: לקח and נתן. Regarding the former he goes on to say:
The form of the perfect is that of a regular Pual and that of the Imperfect is a Pe Nun Hophal; but since these verbs are not found in Piel or Hiphil the above forms are less likely to be survivals of the passives Pual and Hophal. Some grammarians have therefore been led to regard the above forms as examples of a passive Qal.
Waltke and O’Connor
Some cognate languages have something like the Qp (Arabic, Ugaritic, Aramaic) – this adds weight to the arguement for the Qp.
Similarly to Weingreen, IBHS note distinctive regarding roots and Qp forms. Some roots (e.g. לקח) have both suffix forms (i.e. perfect; pointed as Pual) and prefix forms (i.e. imperfect, pointed as Hophal). Others roots (e.g. בזז) have only have suffix; some (e.g. נקם) only have prefix. Sometimes Niphal forms are used (e.g. Job 19:24). Lastly, there are Qp participels (quttal and qittol).
Further Reading: the best place is Introduction to Biblical Hebrew Syntax §22.6.