Why should he have kept a watch on it? He is not a watchman there and it's not like he expected Pratik to steal his nails and play dirty. This is very nice you are conveniently ignoring how pratik actually broke the rules by stealing his nails and putting the onus on Jay. When it's not tejaswi's job to safeguard the nails how is it Jay's by the way? Did the rules not say no one is allowed to touch the equipment? So it's obvious he followed the rules and expected others to do the same simple so I don't find your argument that he should have watched over his nails valid to begin with.
Tomorrow if a robber or some goon holds you at gunpoint asking you to hand over your valuables to him are you going to blame yourself for running into the goon?? Or even better this kind of reminds me of the Khuli tijori analogy used for women whenever we venture out, so as per your logic the one who is wronged or the victim should pay extra attention instead of lashing out and pointing out what has happened, because that is what it seems like going by your post.
We blame victims when we don't want to blame the perpetrator.