when you cast them to the condo's ?? Did you feel the jig hitting the PVC ??
The PVC may not show up very well ... but, the buckets should have !!
Suffice it to say that, if you had trouble "seeing" the PVC, on your DF unit ... others may have a more difficult time finding them. That's a good thing. As long as you have the GPS coord's, and a general triangulation, you should be able to get back on the condos.
Even with a GPS ... I'd still run a "line of sight" mark, between two objects that won't be going anywhere, anytime soon. At least, then, I could line myself up and troll back and forth over the spot ... until I got the DF reading set to pick up the condos (or, at least, the bucket circle). Remember - a 20deg cone angle, in 17ft of water, is only showing a 5ft circle of the bottom ... and even a few seconds of inattention, or a slight breeze, can move your boat off the mark. Dropping a buoy marker, nearby, will help you retain your position ... relative to the condo's .... cp