Last Hot 100 #1 On Vinyl Only?

The good folks in the chart department at Billboard have asked me what the last (most recent) #1
Hot 100 hit was that WAS ONLY COMMERCIALLY RELEASED ON A VINYL 7" SINGLE??? We all figure it had
to be mid-to-late 1980s.

I simply don't have the time to fully research this and I figured that if anyone would have the
answer, it would be someone in this group. Any ideas???

Also, they were wondering about the last Hot 100 to be FULLY made up of vinyl 7" singles only.

When Bryan Adams “Heat Of The Night” was released, it was hailed as
the first cassette single. What I don’t know is whether labels
subsequently released cassette singles of songs already available on
7-inch singles.

They are more interested in the first part of the question (the last #1 on vinyl only) than the second part.

Not sure if they are taking 12" vinyl into the equation (probably not).

I'm guessing the #1 would be somewhere in 1987 or 1988???

O.K., after giving it a little more thought, I don't remember seeing a cassette single on Bob Seger's
"Shakedown". That hit #1 on August 1, 1987. See if anyone can come up with a later #1 that didn't issue a
cassette single. I was not a fan of cassette singles, so there. -Bill.

Billboard started marking the Hot 100 with (C) for
cassette singles in mid-1988, and scanning through the
remainder of 1988 and 1989, it looks like everything had a
cassette single available, so safe to say the last mass
market vinyl-only #1 came out before then.

And there's another technicality to add to Aaron's
examples from the 2020s, I'd also consider 45s from the
Hot 100's "post-single" era starting in 1998. Lots of
hits weren't available commercially on CD/cassette but
were available on vinyl. While these 45s were mainly for
jukebox operators, I'd argue they were "commercial" --
e.g., UPCs, some retail availability, etc. Rob Thomas'
"Lonely No More" might be the last example of a #1 before
the majors stopped supplying jukeboxes.