Please grant me an accurate explanation of diode reverse bias mechanism 
Consider the image above.
Now I am an electron in that depletion region. I was not here initially, I was in the wire (free-moving electron of a copper atom) or perhaps battery (...of an ion?) but now I have been pushed here. 
I feel attracted to the positive charges (which are for example phosphorous atoms with four valence electrons, hence the + charge) at the same time I also feel the repulsion from the negative terminal of the battery. I feel tempted (as well as all my electron friends) to move across the border and happily combine with the phosphorous ions, which is not happening. So what stops me there??
Update: I am expecting to see answers that require knowledge about solid state physics particularly band gap and band theory, which I do not know enough about and need to get a lot more reading. Can anyone please confirm this so I can move on feeling a little more assured and come back to this after I know enough about solid state physics.
 A: I won't try to answer your whole question, because it would take a couple of book chapters. But I'll try to address what seems to be your main misunderstanding.

why am I immobile? (I refer myself to one of the electrons in there) What makes me immobile?

If you're an (conduction band) electron or (valence band) hole, you aren't immobile. You're just not in the depletion region to begin with. The depletion region doesn't block current by making carriers immobile, it blocks current by not having any mobile carriers in it.
If a mobile carrier is somehow introduced into the depletion region, it will produce a current. This is exactly how photodiodes work. Light falling on the depletion region excites electron-hole pairs. The field in the depletion region sweeps the two carriers in opposite direction, and we call it "photocurrent".
A: The title of your question mentions a "reverse bias mechanism", but in the text of your question there is no reference to it nor do you explain what you mean by "reverse bias mechanism". 
Your question seems to boil down to why the electrons do not recombine with the ionized donors in the depletion zone. This is very easily answered. Electrons can be bound to an ionized donor in the semiconductor crystal lattice much like an electron is bound to a proton in a hydrogen atom and it can be calculated in a similar way. The main difference lies in the much lower binding energy (or ionization) of the electron to the ion due to the much larger effective permittivity of the semiconductor and the lower effective mass of the electrons in the crystal. The ionization energy of phosphorus is only about 45meV which is comparable to the thermal energy kT at room temperature. Therefore at room temperature, according to the Fermi occupation statistics, most phosphorus donors are ionized, i.e., they have released their electron into the conduction band. Going to lower temperatures, more and more P ions will catch an electron, become neutral and thus do not act as an active dopant any longer. This is the so-called donor freeze-out.  
