Apparently he did commit suicide from the sources that I've read.
"According to Pudon's account, the Chinese were unable to answer these charges and remained silent. The king declared that the position of the Indian gradualists was victorious and decreed that henceforth the teachings of Heshang Moheyan should be banned. The members of the Chinese faction acknowledged their defeat and returned home to China. Pudon adds that Heshang Moheyan was so upset by his loss of face that he committed suicide with a number of his followers. Kamalasila, however, was not able to savor his victory for long, because some surviving disciples of Heshang hired Chinese assassins to kill him. Pudon states that they murdered Kamalasila by squeezing his kidneys." page 152
-- Introduction to Tibetan Buddhism by John Powers
2007 Snow Lion Publications
Also if you've read the book "Studies in Ch`an and Hua Yen" by Peter N. Gregory, he seems to outline the debate very specifically between Kamalasila & Heshang.
Heshang will begin the debate by stating: If one commits good or bad deeds, one (merely) reaches the higher or lower states of rebirth (respectively). Therefore, he does not attain deliverance from samsara, and the attainment of buddhahood is blocked. An example: White and black clouds alike obscure the sky. But he who does not think, he who does not wish, will be fully delivered from Samsara. He who does not think, not reflect, not investigate, brings about non-perception. By this, one enters (buddhahood) spontaneously (cig car du ‘jug pa). He is like a bodhisattva who dwells on the 10th stage.
Kamalasila: If the mere absence of recollection is regarded as sufficient, it follows that a time of faint or intoxicant one attains the state of non-reflection and thereby buddhahood. But without correct analysis, how can we come to the cognition of the non-substantiality of all phenomena? And, without the realization of emptiness, it is impossible to remove the defilements. Therefore, only correct analytical insight can cast away that which erroneously appears.
From Kamalaśīla’s response back to Heshang, he will indicate and argue that this state of ‘absence’ is equivalent to an individual who is drunk or is cast into a state of non-consciousness. He will argue that there is a specific requirement, and that being the ability to have correct analysis or discriminative understanding. Without having the proper mind to distinguish reality, and without the understanding of emptiness, it is impossible for one to remove afflictions. Furthermore, other disciples or followers of Kamalaśīla will suggest that without the proper undertaking of the perfections (pāramitās) how can one generate the merit and mental training to truly realize highest awakening?
The book by Peter Gregory goes through this in great detail. But I'm guessing this could be a contentious issue. However, Gregory, seems to conclude that Heshang definitely did lose. I'm also 90% sure that Gregory did mention the suicide of Heshang afterwards as well. I've read it from numerous sources, so I'm not sure what your take on that is...