More info
How much rain did you get after you planted? How long after planting did you get the rain? A big rain, 1-2" or more right after planting can be as bad as too little of a amount of rain. I don't like to plant right before a big rain is anticipated , and I don't recommend it. I have seen where a airplane sowed rye grass on a harvested field for cover crop and wasn't tilled under and the seed get washed into piles after a "big" rain that night. Another thing again with moisture, how much moisture was available when you planted. Again, theres a zillion different variables.
Give us a few more details, plot size ( acre, half acre, third of a acre, 5 acres?)
Was the seed left over from last year?
Was it tilled under after sowing?
Was it tilled under too deep?
When you say rye are you planting rye or rye grass?