This is exactly what happened to me 4 months ago. She had been working for 3 years (since my son was born) and did not return after her holiday back home. I was unable to contact her.
At first I was still worried if anything happened to her, but later found out she was stealing from me! I was very upset too as I did not treat her bad.
I quit my job eventually as I could not find anyone to look after my son and he felt quite insecure to the EE who helped me while I was still working. I felt very bad that my son had to go through this.
I informed the agent and immigration the termination of her employment (she failed to report duty). Of course, I later learnt from here that I should have sent her a letter to her Indonesian address with double registered mail.
I learnt from this experience and advices from BK moms that a maid is a maid, she can never be our friend; we just do our best as an employer and do not get emotionally involved. Maid will not appreciate your kindness. All I can say is maids are different now.