mms601: In general when arguing, it is always best to look up each opinion at its source. You took this from the Kovetz Teshuvahs which in turn is quoting the Yeshuas Malko, if you would actually learn the sefer in question, you will see that you are understanding it out of context. He does not mean that one cannot rediscover it, rather that since it got lost it is extremely difficult to know for sure what it really is.
Two points to ponder: 1) there were Geonim that still had Techeilis, so clearly it cannot mean as you thing it does. 2) Again, there is no contemporary Gadol that can argue with a Rishon.