You can use either "look forward" or "look downward" in English but the instruction "look forward and downward" is a little confusing because the directions are considered somewhat different from each other.
Another complicating factor is the idiom, "forward and upward" which isn't directly related to physical directions. If you were to say "forward and downward" many people would associate the phrase with the idiom and assume you were invoking some form of wordplay.
The alternative you mention in the comments is much more clear:
Look down in front of you.
This is a relatively common expression and means exactly what you want it to mean. You can also omit "down":
Look in front of you.
Most English speakers will look slightly ahead of themselves and then scan downward looking for the intended object.