Basically I'm looking at which states have or had a 69, 420, 666, or any other numbers that were changed due to sign theft. A simple no implies that sequential numbers just never got that far.
Interstate: 69 yes, 420 never built, 666 no
US: 69 yes, 420 renumbered for unrelated reasons, 666 renumbered 491 in 2003
Alabama: 69 yes, 420 no, 666 no
Alaska: no
Arizona: 69 yes, 420 no, 666 no
Arkansas: 69 yes, 420 no, 666 no
California: 69 renumbered 245 in 1972, 420 no, 666 no
Colorado: 69 yes, 420 no, 666 no
Connecticut: 69 yes, 420 secret (not due to number), 666 secret (ditto)
Delaware: no
Florida: 69 yes, 420 became a county road in the 1980s; signs mostly disappeared by attrition (since Orange County doesn't care much about county road signage) but FDOT continued to replace stolen signs at the eastern SR 50 junction until some time in the mid-2000s, 666 yes
Georgia: 69 became part of 17 in 1957-1959, probably for unrelated reasons, 420 secret or never assigned (but it should have been?), 666 no
Hawaii: no
Idaho: 69 yes, 420 no, 666 no
Illinois: 69 became part of US 52 for unrelated reasons, 420 no, 666 no
Indiana: 69 yes, 420 became part of I-80/94 for unrelated reasons, 666 no
Iowa: 69 renumbered 138 due to US 69, 420 renumbered 968 for unrelated reasons, 666 no
Kansas: 69 renumbered 65 due to US 69, 420 no, 666 no
Kentucky: 69 yes, 420 yes, 666 yes
Louisiana: 69 yes, 420 yes (the Goog shows the first eastbound reassurance was stolen; it's also part of bike route MRT, foo), 666 eliminated for unrelated reasons (? - apparently 5th Street, Berwick)
Maine: 69 yes, 420 no, 666 no
Maryland: 69 disappeared after 1955 for unrelated reasons, 420 same after 1973, 666 same after 1957
Massachusetts: 69 renumbered 71 to match NY, 420 no, 666 no
Michigan: 69 yes, 420 no, 666 no
Minnesota: 69 renumbered 94 due to US 69, 420 no, 666 no
Mississippi: 69 yes, 420 no, 666 no
Missouri: 69 no (briefly assigned but then skipped due to US 69), 420 no, 666 no
Montana: 69 yes, 420 yes, 666 no
Nebraska: 69 yes (replaced 76 in the 1970s), 420 renumbered L45B for unrelated reasons, 666 no
Nevada: 69 renumbered 377 for unrelated reasons, 420 no, 666 no
New Hampshire: 69 no (not sure if there ever was one), 420 no, 666 no
New Jersey: 69 renumbered 31 in the mid-1960s, 420 no, 666 no
New Mexico: 69 disappeared in the 1980s (?) for unrelated reasons, 420 yes (assigned in 1988), 666 no
New York: 69 yes, 420 yes, 666 no
North Carolina: 69 yes, 420 no, 666 no
North Dakota: 69 renumbered 4 in the 1990s, 420 no, 666 no
Ohio: 69 became part of 235 in 1967-1969, 420 yes, 666 yes, 714 renumbered 814 in 1982-1983 (apparently due to Quaaludes, the baby ducksheep drug)
Oklahoma: 69 renumbered 54A, 54B, 183A in 1987-1988 (may have been due to theft or other reasons), 420 no, 666 no
Oregon: 69 renumbered 569 in 2007 before signs were posted, 420 secret (one of only a few highway numbers to not get a (sometimes) signed route designation in the 2000s), was coincidentally the old main road from Klamath Falls to Weed, 666 no
Pennsylvania: 69 yes, 420 yes, 666 yes
Rhode Island: no
South Carolina: 69 renumbered 65 in early 1980s, 420 yes, 666 probably eliminated for unrelated reasons
South Dakota: no (but 420 may have existed, depending on how the 4xx routes are numbered)
Tennessee: 69 yes, 420 yes, 666 no
Texas: 69 renumbered 112 in 1992 "due to numerous thefts of the popular SH 69 signs" (Park Road 69 and Spur 69 still exist, but neither seems to be signed), 420 yes (FM; Loop renumbered US 83 Business for unrelated reasons), 666 yes (FM)
Utah: 69 renumbered 38 in 1993 since "the SR-69 route signs have become a collectors' item for a large number of individuals", 420 no, 666 no
Vermont: 69 no (was there ever one?), 420 no, 666 no
Virginia: 69 yes, 420 secret (not necessarily due to the number), 666 yes (a bunch of secondaries)
Washington: no
West Virginia: 69 yes, 420 no, 666 no
Wisconsin: 69 yes, 420 no, 666 no
Wyoming: 69 no, 420 renumbered for unrelated reasons, 666 no
In total:
69: 8 probably renumbered due to theft, 24 signed
420: 3 possibly purposely unsigned, 10 signed
666: 1 renumbered (as well as at least one county in NJ), 6 signed
714: 1 renumbered due to theft