If you're a bit dehydrated (which can happen with a cold because you're making lots of snot lol) that can raise the baby's heartbeat. I had a similar drama when I was pregnant with DS and had a stomach virus - I got a bit dehydrated, went into hospital for monitoring and his HR was hovering around 190-200. After a night on a drip (no fun) it was fine the next morning and I went home.
It was a bit rough of the midwives not to tell you anything - I HATED it when I was pregnant if I was on monitors and they'd just look at it and not say anything, it's a sure fire way to do a pregnant person's head in! Sometimes they forget that you're hanging on their every word and reaction in a situation like that I think.
I'd probably want to have it checked again as Alan said, but it's likely that it is related to your cold so try not to freak out too much...that won't help bub's heartrate come down either