No worries.
If grass carp were used, and apparently effectively, coontail, hydrilla, pondweeds, and/or naiads were likely in the lake. Grass carp physically can't control American lotus or lilies, those must be treated with herbicide.
We're seeing pretty consistently in Arkansas that triploid grass carp start dying out at about 10 years post-stocking. Before that happens, vegetation reestablishment projects have had a hard time getting going. They nibble away anything that sprouts pretty quick.
What we've also noticed is that the seed banks for hydrilla and coontail can survive for years waiting on favorable conditions (like reduced herbivore populations, clarity improvements, soil disturbance).
It may sound dumb, but I have personally seen and have read some peer-reviewed scientific literature suggesting this might work on a larger scale; consider trying it. When the water gets to the low-mid 50's this spring, go to an area of the lake that was known to grow vegetation in the past and pull something behind a boat that will disturb the mud. Maybe a section of old chain link fence, a big rake, maybe even a water pump contraption with a drag line that will blow the sediment around. Map out a grid that you'll scour (a few 40 x 40 ft areas for example) and make mental notes or save gps waypoints of the edges of the plots. Come back early to mid summer and see if you get some growth in the areas you disturbed. The seeds of some submerged plant species are really sensitive to the depth they are buried and being re-exposed or brought back to the surface of the mud can activate them into sprouting. If your lake had a long history of vegetation growth, there is probably a viable dormant seed bank still down there. If those sprouts in your plot survive to maturity, you have a reproducing crop again and the revegetation will begin. You can check for growth over your disturbed plots really easy with sonar. I have been using down imaging set to 455 khz for a wider beam angle and it's easy to find individual sprouts.
While you have those test plots in one part of the lake, you can actively plant in others to compare results. You should try some protected enclosures set 2-4 feet deep with whichever plants you end up choosing planted within them. There may still be some carp left in the system, and there are always turtles that will nibble on new sprouts or common carp that will inadvertently disturb the sprouts while feeding on muck so protected enclosures are usually necessary to establish founder colonies. There is an awesome publication on reestablishing vegetation in reservoirs published by Texas Parks and Wildlife that we've been using to help guide some projects in Arkansas that are working:
https://tpwd.texas.gov/publications/pwdpubs/media/pwd_rp_t3200_1770.pdf. Diagrams of enclosures start on page 28. On page 52 they have listed a few sources for native aquatic plants, these suppliers may know folks that could do the work for you as well.
THAT SAID; vegetation was a problem before and it will become a problem again if left unchecked. Look into the pondweeds (sago, American, waterthread), wild celery (eel grass/vallisneria), or coontail for submerged plants. White water lily (fragrant water lily) is generally considered easier to control than American lotus; it doesn't grow as deep or spread as fast from what I have seen.
Make sure you have approval from all parties who have interest in the lake before proceeding with this.
You'll not find a legal source of hydrilla and please do not try to harvest/transport it from a public fishery. The species mentioned above will do you fine.
When plants get established again, don't rule out putting in maybe 1 grass carp per vegetated acre every 5 or so years just to help keep things from getting out of control. That, or be ready for periodic herbicide applications (that will be way more expensive and labor intensive than grass carp). Grass carp are an excellent tool, but they have to be used very carefully.
There are a few other experts that come through the forum from time to time. Hope to hear their take.
Also, please share updates from time to time.