Jessie,
My suggestion, get several space rocks, I go with the the more the merrier, and spread them about the yard. Get a scope and start around midnight stargazing and searching. I don't know if either one matters, but I would switch between them. Stay out until four o'clock, I have always had mine abducted after 3:00 so give it to four and if no show, try again the next night.
My one sim was abducted several times before he became pregnant, and the other was abducted and on the second abduction he was pregnant.
Good luck,