In fact, it seems that forgery has been used, although this term and its negative connotations might be completely out of place in classical India. The first example one might think of is Madhva, who quoted profusely from texts which have not been traced. If he really forged his quoted, Madhva would seem to me a unique case in the Classical Indian horizon —I still do not understand why he did not just interpret the texts he had at his disposal in the way he wanted.

Now, one might object, Madhva’s case is not that exceptional, given that many other authors founded their teachings on lost texts. Mīmāṃsā authors justified the validity of Smṛtis and even of sadācāra ‘the behaviour of right people’ exactly by postulating that they are founded on lost Vedic texts, or on only-inferable ones (nityānumeya). But this is not a suitable comparison.
In fact, on the one hand we have Mīmāṃsā and Dharmaśāstra (and later also Vedānta) authors trying to justify existing behaviours on the basis of inferred texts, on the other we have Madhva trying to ground new ideas on the basis of untraced but existing quotes.
Thus, Madhva is more or less doing the opposite of what Kumārila and Co. were doing.
However, what about Madhva’s successors and supporters, both within and without his school (e.g., the Gauḍīya Jīva Gosvāmī)? In this case, could the fact that the idea of lost Vedas was already current have helped in making the claim that Madhva had quoted from texts which were later lost less preposterous?
Perhaps. But I tend to doubt it, given that the claim of loss texts seems to be always projected to a far-away antiquity, and more specifically to the Vedas (including texts contemporary scholars would not recognise as part of the Veda, but which were presented as such, like the Pāñcarātra Ekāyanaveda). Also the gter ma-device of “finding” back (allegedly) lost Buddhist texts had a different purpose (namely legitimizing whole new texts).
Madhva and his followers, as far as I know, never used the lost Veda argument to support their claims. This might be a further indirect evidence of the fact that they also thought of the two cases as quite far apart.

What do you think? Did you ever encounter “forged” texts in Classical Indian Philosophy?

On Madhva’s quotes, see this post.

Cross-posted on The Indian Philosophy Blog, where you can also read several interesting comments.