Is a mother entitled to know what happened to the money that was given to her adult son, and is it permissible to conceal the loss of the money from her for fear of her anger?

What the mother gave to her son is a complete gift (hiba) upon its full possession, and the mature, sane, and رشيد (of sound judgment) son's disposal of it is permissible. His spending of it on good deeds and buying clothes, if it does not deviate from custom and common practice, is not extravagance (israf); otherwise, it is blameworthy extravagance. As for his loss in trade, anyone is susceptible to it, and he should strive to recover the amount that caused the loss to the best of his ability. He should not inform his mother of the true extent of the loss if she asks him, in order to avoid causing her distress, and he may tell her that the money is still there. This is with the caveat that celebrating birthdays is not permissible.