The use of hygroscopic products to speed up drying is actually based on a misconception, or at least, not as effective as you might think.
The rate of evaporation is proportional to the product D*(p_vp-p_env), where D is the diffusion coefficient of the vapor molecules in air, p_vp the vapor pressure (partial pressure of saturated vapor), and p_env the partial pressure of vapor in the environment.
A desiccant will lower p_env to zero, so it will help a bit; for example, the p difference is (2.4-1.2) kPa at 20 C, 50% relative humidity, increasing to (2.4-0) with a desiccant, a factor 2 increase. However, putting it in a warm place will increase both D (a bit) and p_vp (a lot). Heating it to 50 C in the same environment will increase the p difference to (12.3-1.2), a factor 9 increase. Additionally, D will increase by a factor 1.2. A phone that is switched off should be able to handle such temperatures, so putting it on top of the cable modem is cheaper and more effective.
Even better would be to dry it in vacuum; that will increase the D parameter tremendously. But most people don't have that at home, although I suppose that some creativity with a wine preserver pump might get you somewhere.